(function(f){if(typeof exports==="object"&&typeof module!=="undefined"){module.exports=f()}else if(typeof define==="function"&&define.amd){define([],f)}else{var g;if(typeof window!=="undefined"){g=window}else if(typeof global!=="undefined"){g=global}else if(typeof self!=="undefined"){g=self}else{g=this}g.adapter = f()}})(function(){var define,module,exports;return (function e(t,n,r){function s(o,u){if(!n[o]){if(!t[o]){var a=typeof require=="function"&&require;if(!u&&a)return a(o,!0);if(i)return i(o,!0);var f=new Error("Cannot find module '"+o+"'");throw f.code="MODULE_NOT_FOUND",f}var l=n[o]={exports:{}};t[o][0].call(l.exports,function(e){var n=t[o][1][e];return s(n?n:e)},l,l.exports,e,t,n,r)}return n[o].exports}var i=typeof require=="function"&&require;for(var o=0;o<r.length;o++)s(r[o]);return s})({1:[function(require,module,exports){
  /*
   *  Copyright (c) 2017 The WebRTC project authors. All Rights Reserved.
   *
   *  Use of this source code is governed by a BSD-style license
   *  that can be found in the LICENSE file in the root of the source
   *  tree.
   */
  /* eslint-env node */
    'use strict';

    var SDPUtils = require('sdp');

    function fixStatsType(stat) {
        return {
                inboundrtp: 'inbound-rtp',
                outboundrtp: 'outbound-rtp',
                candidatepair: 'candidate-pair',
                localcandidate: 'local-candidate',
                remotecandidate: 'remote-candidate'
            }[stat.type] || stat.type;
    }

    function writeMediaSection(transceiver, caps, type, stream, dtlsRole) {
        var sdp = SDPUtils.writeRtpDescription(transceiver.kind, caps);

        // Map ICE parameters (ufrag, pwd) to SDP.
        sdp += SDPUtils.writeIceParameters(
            transceiver.iceGatherer.getLocalParameters());

        // Map DTLS parameters to SDP.
        sdp += SDPUtils.writeDtlsParameters(
            transceiver.dtlsTransport.getLocalParameters(),
            type === 'offer' ? 'actpass' : dtlsRole || 'active');

        sdp += 'a=mid:' + transceiver.mid + '\r\n';

        if (transceiver.rtpSender && transceiver.rtpReceiver) {
            sdp += 'a=sendrecv\r\n';
        } else if (transceiver.rtpSender) {
            sdp += 'a=sendonly\r\n';
        } else if (transceiver.rtpReceiver) {
            sdp += 'a=recvonly\r\n';
        } else {
            sdp += 'a=inactive\r\n';
        }

        if (transceiver.rtpSender) {
            var trackId = transceiver.rtpSender._initialTrackId ||
                transceiver.rtpSender.track.id;
            transceiver.rtpSender._initialTrackId = trackId;
            // spec.
            var msid = 'msid:' + (stream ? stream.id : '-') + ' ' +
                trackId + '\r\n';
            sdp += 'a=' + msid;
            // for Chrome. Legacy should no longer be required.
            sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].ssrc +
                ' ' + msid;

            // RTX
            if (transceiver.sendEncodingParameters[0].rtx) {
                sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].rtx.ssrc +
                    ' ' + msid;
                sdp += 'a=ssrc-group:FID ' +
                    transceiver.sendEncodingParameters[0].ssrc + ' ' +
                    transceiver.sendEncodingParameters[0].rtx.ssrc +
                    '\r\n';
            }
        }
        // FIXME: this should be written by writeRtpDescription.
        sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].ssrc +
            ' cname:' + SDPUtils.localCName + '\r\n';
        if (transceiver.rtpSender && transceiver.sendEncodingParameters[0].rtx) {
            sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].rtx.ssrc +
                ' cname:' + SDPUtils.localCName + '\r\n';
        }
        return sdp;
    }

// Edge does not like
// 1) stun: filtered after 14393 unless ?transport=udp is present
// 2) turn: that does not have all of turn:host:port?transport=udp
// 3) turn: with ipv6 addresses
// 4) turn: occurring muliple times
    function filterIceServers(iceServers, edgeVersion) {
        var hasTurn = false;
        iceServers = JSON.parse(JSON.stringify(iceServers));
        return iceServers.filter(function(server) {
            if (server && (server.urls || server.url)) {
                var urls = server.urls || server.url;
                if (server.url && !server.urls) {
                    console.warn('RTCIceServer.url is deprecated! Use urls instead.');
                }
                var isString = typeof urls === 'string';
                if (isString) {
                    urls = [urls];
                }
                urls = urls.filter(function(url) {
                    var validTurn = url.indexOf('turn:') === 0 &&
                        url.indexOf('transport=udp') !== -1 &&
                        url.indexOf('turn:[') === -1 &&
                        !hasTurn;

                    if (validTurn) {
                        hasTurn = true;
                        return true;
                    }
                    return url.indexOf('stun:') === 0 && edgeVersion >= 14393 &&
                        url.indexOf('?transport=udp') === -1;
                });

                delete server.url;
                server.urls = isString ? urls[0] : urls;
                return !!urls.length;
            }
        });
    }

// Determines the intersection of local and remote capabilities.
    function getCommonCapabilities(localCapabilities, remoteCapabilities) {
        var commonCapabilities = {
            codecs: [],
            headerExtensions: [],
            fecMechanisms: []
        };

        var findCodecByPayloadType = function(pt, codecs) {
            pt = parseInt(pt, 10);
            for (var i = 0; i < codecs.length; i++) {
                if (codecs[i].payloadType === pt ||
                    codecs[i].preferredPayloadType === pt) {
                    return codecs[i];
                }
            }
        };

        var rtxCapabilityMatches = function(lRtx, rRtx, lCodecs, rCodecs) {
            var lCodec = findCodecByPayloadType(lRtx.parameters.apt, lCodecs);
            var rCodec = findCodecByPayloadType(rRtx.parameters.apt, rCodecs);
            return lCodec && rCodec &&
                lCodec.name.toLowerCase() === rCodec.name.toLowerCase();
        };

        localCapabilities.codecs.forEach(function(lCodec) {
            for (var i = 0; i < remoteCapabilities.codecs.length; i++) {
                var rCodec = remoteCapabilities.codecs[i];
                if (lCodec.name.toLowerCase() === rCodec.name.toLowerCase() &&
                    lCodec.clockRate === rCodec.clockRate) {
                    if (lCodec.name.toLowerCase() === 'rtx' &&
                        lCodec.parameters && rCodec.parameters.apt) {
                        // for RTX we need to find the local rtx that has a apt
                        // which points to the same local codec as the remote one.
                        if (!rtxCapabilityMatches(lCodec, rCodec,
                                localCapabilities.codecs, remoteCapabilities.codecs)) {
                            continue;
                        }
                    }
                    rCodec = JSON.parse(JSON.stringify(rCodec)); // deepcopy
                    // number of channels is the highest common number of channels
                    rCodec.numChannels = Math.min(lCodec.numChannels,
                        rCodec.numChannels);
                    // push rCodec so we reply with offerer payload type
                    commonCapabilities.codecs.push(rCodec);

                    // determine common feedback mechanisms
                    rCodec.rtcpFeedback = rCodec.rtcpFeedback.filter(function(fb) {
                        for (var j = 0; j < lCodec.rtcpFeedback.length; j++) {
                            if (lCodec.rtcpFeedback[j].type === fb.type &&
                                lCodec.rtcpFeedback[j].parameter === fb.parameter) {
                                return true;
                            }
                        }
                        return false;
                    });
                    // FIXME: also need to determine .parameters
                    //  see https://github.com/openpeer/ortc/issues/569
                    break;
                }
            }
        });

        localCapabilities.headerExtensions.forEach(function(lHeaderExtension) {
            for (var i = 0; i < remoteCapabilities.headerExtensions.length;
                 i++) {
                var rHeaderExtension = remoteCapabilities.headerExtensions[i];
                if (lHeaderExtension.uri === rHeaderExtension.uri) {
                    commonCapabilities.headerExtensions.push(rHeaderExtension);
                    break;
                }
            }
        });

        // FIXME: fecMechanisms
        return commonCapabilities;
    }

// is action=setLocalDescription with type allowed in signalingState
    function isActionAllowedInSignalingState(action, type, signalingState) {
        return {
                offer: {
                    setLocalDescription: ['stable', 'have-local-offer'],
                    setRemoteDescription: ['stable', 'have-remote-offer']
                },
                answer: {
                    setLocalDescription: ['have-remote-offer', 'have-local-pranswer'],
                    setRemoteDescription: ['have-local-offer', 'have-remote-pranswer']
                }
            }[type][action].indexOf(signalingState) !== -1;
    }

    function maybeAddCandidate(iceTransport, candidate) {
        // Edge's internal representation adds some fields therefore
        // not all fieldѕ are taken into account.
        var alreadyAdded = iceTransport.getRemoteCandidates()
            .find(function(remoteCandidate) {
                return candidate.foundation === remoteCandidate.foundation &&
                    candidate.ip === remoteCandidate.ip &&
                    candidate.port === remoteCandidate.port &&
                    candidate.priority === remoteCandidate.priority &&
                    candidate.protocol === remoteCandidate.protocol &&
                    candidate.type === remoteCandidate.type;
            });
        if (!alreadyAdded) {
            iceTransport.addRemoteCandidate(candidate);
        }
        return !alreadyAdded;
    }


    function makeError(name, description) {
        var e = new Error(description);
        e.name = name;
        // legacy error codes from https://heycam.github.io/webidl/#idl-DOMException-error-names
        e.code = {
            NotSupportedError: 9,
            InvalidStateError: 11,
            InvalidAccessError: 15,
            TypeError: undefined,
            OperationError: undefined
        }[name];
        return e;
    }

    module.exports = function(window, edgeVersion) {
        // https://w3c.github.io/mediacapture-main/#mediastream
        // Helper function to add the track to the stream and
        // dispatch the event ourselves.
        function addTrackToStreamAndFireEvent(track, stream) {
            stream.addTrack(track);
            stream.dispatchEvent(new window.MediaStreamTrackEvent('addtrack',
                {track: track}));
        }

        function removeTrackFromStreamAndFireEvent(track, stream) {
            stream.removeTrack(track);
            stream.dispatchEvent(new window.MediaStreamTrackEvent('removetrack',
                {track: track}));
        }

        function fireAddTrack(pc, track, receiver, streams) {
            var trackEvent = new Event('track');
            trackEvent.track = track;
            trackEvent.receiver = receiver;
            trackEvent.transceiver = {receiver: receiver};
            trackEvent.streams = streams;
            window.setTimeout(function() {
                pc._dispatchEvent('track', trackEvent);
            });
        }

        var RTCPeerConnection = function(config) {
            var pc = this;

            var _eventTarget = document.createDocumentFragment();
            ['addEventListener', 'removeEventListener', 'dispatchEvent']
                .forEach(function(method) {
                    pc[method] = _eventTarget[method].bind(_eventTarget);
                });

            this.canTrickleIceCandidates = null;

            this.needNegotiation = false;

            this.localStreams = [];
            this.remoteStreams = [];

            this.localDescription = null;
            this.remoteDescription = null;

            this.signalingState = 'stable';
            this.iceConnectionState = 'new';
            this.connectionState = 'new';
            this.iceGatheringState = 'new';

            config = JSON.parse(JSON.stringify(config || {}));

            this.usingBundle = config.bundlePolicy === 'max-bundle';
            if (config.rtcpMuxPolicy === 'negotiate') {
                throw(makeError('NotSupportedError',
                    'rtcpMuxPolicy \'negotiate\' is not supported'));
            } else if (!config.rtcpMuxPolicy) {
                config.rtcpMuxPolicy = 'require';
            }

            switch (config.iceTransportPolicy) {
                case 'all':
                case 'relay':
                    break;
                default:
                    config.iceTransportPolicy = 'all';
                    break;
            }

            switch (config.bundlePolicy) {
                case 'balanced':
                case 'max-compat':
                case 'max-bundle':
                    break;
                default:
                    config.bundlePolicy = 'balanced';
                    break;
            }

            config.iceServers = filterIceServers(config.iceServers || [], edgeVersion);

            this._iceGatherers = [];
            if (config.iceCandidatePoolSize) {
                for (var i = config.iceCandidatePoolSize; i > 0; i--) {
                    this._iceGatherers.push(new window.RTCIceGatherer({
                        iceServers: config.iceServers,
                        gatherPolicy: config.iceTransportPolicy
                    }));
                }
            } else {
                config.iceCandidatePoolSize = 0;
            }

            this._config = config;

            // per-track iceGathers, iceTransports, dtlsTransports, rtpSenders, ...
            // everything that is needed to describe a SDP m-line.
            this.transceivers = [];

            this._sdpSessionId = SDPUtils.generateSessionId();
            this._sdpSessionVersion = 0;

            this._dtlsRole = undefined; // role for a=setup to use in answers.

            this._isClosed = false;
        };

        // set up event handlers on prototype
        RTCPeerConnection.prototype.onicecandidate = null;
        RTCPeerConnection.prototype.onaddstream = null;
        RTCPeerConnection.prototype.ontrack = null;
        RTCPeerConnection.prototype.onremovestream = null;
        RTCPeerConnection.prototype.onsignalingstatechange = null;
        RTCPeerConnection.prototype.oniceconnectionstatechange = null;
        RTCPeerConnection.prototype.onconnectionstatechange = null;
        RTCPeerConnection.prototype.onicegatheringstatechange = null;
        RTCPeerConnection.prototype.onnegotiationneeded = null;
        RTCPeerConnection.prototype.ondatachannel = null;

        RTCPeerConnection.prototype._dispatchEvent = function(name, event) {
            if (this._isClosed) {
                return;
            }
            this.dispatchEvent(event);
            if (typeof this['on' + name] === 'function') {
                this['on' + name](event);
            }
        };

        RTCPeerConnection.prototype._emitGatheringStateChange = function() {
            var event = new Event('icegatheringstatechange');
            this._dispatchEvent('icegatheringstatechange', event);
        };

        RTCPeerConnection.prototype.getConfiguration = function() {
            return this._config;
        };

        RTCPeerConnection.prototype.getLocalStreams = function() {
            return this.localStreams;
        };

        RTCPeerConnection.prototype.getRemoteStreams = function() {
            return this.remoteStreams;
        };

        // internal helper to create a transceiver object.
        // (which is not yet the same as the WebRTC 1.0 transceiver)
        RTCPeerConnection.prototype._createTransceiver = function(kind, doNotAdd) {
            var hasBundleTransport = this.transceivers.length > 0;
            var transceiver = {
                track: null,
                iceGatherer: null,
                iceTransport: null,
                dtlsTransport: null,
                localCapabilities: null,
                remoteCapabilities: null,
                rtpSender: null,
                rtpReceiver: null,
                kind: kind,
                mid: null,
                sendEncodingParameters: null,
                recvEncodingParameters: null,
                stream: null,
                associatedRemoteMediaStreams: [],
                wantReceive: true
            };
            if (this.usingBundle && hasBundleTransport) {
                transceiver.iceTransport = this.transceivers[0].iceTransport;
                transceiver.dtlsTransport = this.transceivers[0].dtlsTransport;
            } else {
                var transports = this._createIceAndDtlsTransports();
                transceiver.iceTransport = transports.iceTransport;
                transceiver.dtlsTransport = transports.dtlsTransport;
            }
            if (!doNotAdd) {
                this.transceivers.push(transceiver);
            }
            return transceiver;
        };

        RTCPeerConnection.prototype.addTrack = function(track, stream) {
            if (this._isClosed) {
                throw makeError('InvalidStateError',
                    'Attempted to call addTrack on a closed peerconnection.');
            }

            var alreadyExists = this.transceivers.find(function(s) {
                return s.track === track;
            });

            if (alreadyExists) {
                throw makeError('InvalidAccessError', 'Track already exists.');
            }

            var transceiver;
            for (var i = 0; i < this.transceivers.length; i++) {
                if (!this.transceivers[i].track &&
                    this.transceivers[i].kind === track.kind) {
                    transceiver = this.transceivers[i];
                }
            }
            if (!transceiver) {
                transceiver = this._createTransceiver(track.kind);
            }

            this._maybeFireNegotiationNeeded();

            if (this.localStreams.indexOf(stream) === -1) {
                this.localStreams.push(stream);
            }

            transceiver.track = track;
            transceiver.stream = stream;
            transceiver.rtpSender = new window.RTCRtpSender(track,
                transceiver.dtlsTransport);
            return transceiver.rtpSender;
        };

        RTCPeerConnection.prototype.addStream = function(stream) {
            var pc = this;
            if (edgeVersion >= 15025) {
                stream.getTracks().forEach(function(track) {
                    pc.addTrack(track, stream);
                });
            } else {
                // Clone is necessary for local demos mostly, attaching directly
                // to two different senders does not work (build 10547).
                // Fixed in 15025 (or earlier)
                var clonedStream = stream.clone();
                stream.getTracks().forEach(function(track, idx) {
                    var clonedTrack = clonedStream.getTracks()[idx];
                    track.addEventListener('enabled', function(event) {
                        clonedTrack.enabled = event.enabled;
                    });
                });
                clonedStream.getTracks().forEach(function(track) {
                    pc.addTrack(track, clonedStream);
                });
            }
        };

        RTCPeerConnection.prototype.removeTrack = function(sender) {
            if (this._isClosed) {
                throw makeError('InvalidStateError',
                    'Attempted to call removeTrack on a closed peerconnection.');
            }

            if (!(sender instanceof window.RTCRtpSender)) {
                throw new TypeError('Argument 1 of RTCPeerConnection.removeTrack ' +
                    'does not implement interface RTCRtpSender.');
            }

            var transceiver = this.transceivers.find(function(t) {
                return t.rtpSender === sender;
            });

            if (!transceiver) {
                throw makeError('InvalidAccessError',
                    'Sender was not created by this connection.');
            }
            var stream = transceiver.stream;

            transceiver.rtpSender.stop();
            transceiver.rtpSender = null;
            transceiver.track = null;
            transceiver.stream = null;

            // remove the stream from the set of local streams
            var localStreams = this.transceivers.map(function(t) {
                return t.stream;
            });
            if (localStreams.indexOf(stream) === -1 &&
                this.localStreams.indexOf(stream) > -1) {
                this.localStreams.splice(this.localStreams.indexOf(stream), 1);
            }

            this._maybeFireNegotiationNeeded();
        };

        RTCPeerConnection.prototype.removeStream = function(stream) {
            var pc = this;
            stream.getTracks().forEach(function(track) {
                var sender = pc.getSenders().find(function(s) {
                    return s.track === track;
                });
                if (sender) {
                    pc.removeTrack(sender);
                }
            });
        };

        RTCPeerConnection.prototype.getSenders = function() {
            return this.transceivers.filter(function(transceiver) {
                return !!transceiver.rtpSender;
            })
                .map(function(transceiver) {
                    return transceiver.rtpSender;
                });
        };

        RTCPeerConnection.prototype.getReceivers = function() {
            return this.transceivers.filter(function(transceiver) {
                return !!transceiver.rtpReceiver;
            })
                .map(function(transceiver) {
                    return transceiver.rtpReceiver;
                });
        };


        RTCPeerConnection.prototype._createIceGatherer = function(sdpMLineIndex,
                                                                  usingBundle) {
            var pc = this;
            if (usingBundle && sdpMLineIndex > 0) {
                return this.transceivers[0].iceGatherer;
            } else if (this._iceGatherers.length) {
                return this._iceGatherers.shift();
            }
            var iceGatherer = new window.RTCIceGatherer({
                iceServers: this._config.iceServers,
                gatherPolicy: this._config.iceTransportPolicy
            });
            Object.defineProperty(iceGatherer, 'state',
                {value: 'new', writable: true}
            );

            this.transceivers[sdpMLineIndex].bufferedCandidateEvents = [];
            this.transceivers[sdpMLineIndex].bufferCandidates = function(event) {
                var end = !event.candidate || Object.keys(event.candidate).length === 0;
                // polyfill since RTCIceGatherer.state is not implemented in
                // Edge 10547 yet.
                iceGatherer.state = end ? 'completed' : 'gathering';
                if (pc.transceivers[sdpMLineIndex].bufferedCandidateEvents !== null) {
                    pc.transceivers[sdpMLineIndex].bufferedCandidateEvents.push(event);
                }
            };
            iceGatherer.addEventListener('localcandidate',
                this.transceivers[sdpMLineIndex].bufferCandidates);
            return iceGatherer;
        };

        // start gathering from an RTCIceGatherer.
        RTCPeerConnection.prototype._gather = function(mid, sdpMLineIndex) {
            var pc = this;
            var iceGatherer = this.transceivers[sdpMLineIndex].iceGatherer;
            if (iceGatherer.onlocalcandidate) {
                return;
            }
            var bufferedCandidateEvents =
                this.transceivers[sdpMLineIndex].bufferedCandidateEvents;
            this.transceivers[sdpMLineIndex].bufferedCandidateEvents = null;
            iceGatherer.removeEventListener('localcandidate',
                this.transceivers[sdpMLineIndex].bufferCandidates);
            iceGatherer.onlocalcandidate = function(evt) {
                if (pc.usingBundle && sdpMLineIndex > 0) {
                    // if we know that we use bundle we can drop candidates with
                    // ѕdpMLineIndex > 0. If we don't do this then our state gets
                    // confused since we dispose the extra ice gatherer.
                    return;
                }
                var event = new Event('icecandidate');
                event.candidate = {sdpMid: mid, sdpMLineIndex: sdpMLineIndex};

                var cand = evt.candidate;
                // Edge emits an empty object for RTCIceCandidateComplete‥
                var end = !cand || Object.keys(cand).length === 0;
                if (end) {
                    // polyfill since RTCIceGatherer.state is not implemented in
                    // Edge 10547 yet.
                    if (iceGatherer.state === 'new' || iceGatherer.state === 'gathering') {
                        iceGatherer.state = 'completed';
                    }
                } else {
                    if (iceGatherer.state === 'new') {
                        iceGatherer.state = 'gathering';
                    }
                    // RTCIceCandidate doesn't have a component, needs to be added
                    cand.component = 1;
                    // also the usernameFragment. TODO: update SDP to take both variants.
                    cand.ufrag = iceGatherer.getLocalParameters().usernameFragment;

                    var serializedCandidate = SDPUtils.writeCandidate(cand);
                    event.candidate = Object.assign(event.candidate,
                        SDPUtils.parseCandidate(serializedCandidate));

                    event.candidate.candidate = serializedCandidate;
                    event.candidate.toJSON = function() {
                        return {
                            candidate: event.candidate.candidate,
                            sdpMid: event.candidate.sdpMid,
                            sdpMLineIndex: event.candidate.sdpMLineIndex,
                            usernameFragment: event.candidate.usernameFragment
                        };
                    };
                }

                // update local description.
                var sections = SDPUtils.getMediaSections(pc.localDescription.sdp);
                if (!end) {
                    sections[event.candidate.sdpMLineIndex] +=
                        'a=' + event.candidate.candidate + '\r\n';
                } else {
                    sections[event.candidate.sdpMLineIndex] +=
                        'a=end-of-candidates\r\n';
                }
                pc.localDescription.sdp =
                    SDPUtils.getDescription(pc.localDescription.sdp) +
                    sections.join('');
                var complete = pc.transceivers.every(function(transceiver) {
                    return transceiver.iceGatherer &&
                        transceiver.iceGatherer.state === 'completed';
                });

                if (pc.iceGatheringState !== 'gathering') {
                    pc.iceGatheringState = 'gathering';
                    pc._emitGatheringStateChange();
                }

                // Emit candidate. Also emit null candidate when all gatherers are
                // complete.
                if (!end) {
                    pc._dispatchEvent('icecandidate', event);
                }
                if (complete) {
                    pc._dispatchEvent('icecandidate', new Event('icecandidate'));
                    pc.iceGatheringState = 'complete';
                    pc._emitGatheringStateChange();
                }
            };

            // emit already gathered candidates.
            window.setTimeout(function() {
                bufferedCandidateEvents.forEach(function(e) {
                    iceGatherer.onlocalcandidate(e);
                });
            }, 0);
        };

        // Create ICE transport and DTLS transport.
        RTCPeerConnection.prototype._createIceAndDtlsTransports = function() {
            var pc = this;
            var iceTransport = new window.RTCIceTransport(null);
            iceTransport.onicestatechange = function() {
                pc._updateIceConnectionState();
                pc._updateConnectionState();
            };

            var dtlsTransport = new window.RTCDtlsTransport(iceTransport);
            dtlsTransport.ondtlsstatechange = function() {
                pc._updateConnectionState();
            };
            dtlsTransport.onerror = function() {
                // onerror does not set state to failed by itself.
                Object.defineProperty(dtlsTransport, 'state',
                    {value: 'failed', writable: true});
                pc._updateConnectionState();
            };

            return {
                iceTransport: iceTransport,
                dtlsTransport: dtlsTransport
            };
        };

        // Destroy ICE gatherer, ICE transport and DTLS transport.
        // Without triggering the callbacks.
        RTCPeerConnection.prototype._disposeIceAndDtlsTransports = function(
            sdpMLineIndex) {
            var iceGatherer = this.transceivers[sdpMLineIndex].iceGatherer;
            if (iceGatherer) {
                delete iceGatherer.onlocalcandidate;
                delete this.transceivers[sdpMLineIndex].iceGatherer;
            }
            var iceTransport = this.transceivers[sdpMLineIndex].iceTransport;
            if (iceTransport) {
                delete iceTransport.onicestatechange;
                delete this.transceivers[sdpMLineIndex].iceTransport;
            }
            var dtlsTransport = this.transceivers[sdpMLineIndex].dtlsTransport;
            if (dtlsTransport) {
                delete dtlsTransport.ondtlsstatechange;
                delete dtlsTransport.onerror;
                delete this.transceivers[sdpMLineIndex].dtlsTransport;
            }
        };

        // Start the RTP Sender and Receiver for a transceiver.
        RTCPeerConnection.prototype._transceive = function(transceiver,
                                                           send, recv) {
            var params = getCommonCapabilities(transceiver.localCapabilities,
                transceiver.remoteCapabilities);
            if (send && transceiver.rtpSender) {
                params.encodings = transceiver.sendEncodingParameters;
                params.rtcp = {
                    cname: SDPUtils.localCName,
                    compound: transceiver.rtcpParameters.compound
                };
                if (transceiver.recvEncodingParameters.length) {
                    params.rtcp.ssrc = transceiver.recvEncodingParameters[0].ssrc;
                }
                transceiver.rtpSender.send(params);
            }
            if (recv && transceiver.rtpReceiver && params.codecs.length > 0) {
                // remove RTX field in Edge 14942
                if (transceiver.kind === 'video'
                    && transceiver.recvEncodingParameters
                    && edgeVersion < 15019) {
                    transceiver.recvEncodingParameters.forEach(function(p) {
                        delete p.rtx;
                    });
                }
                if (transceiver.recvEncodingParameters.length) {
                    params.encodings = transceiver.recvEncodingParameters;
                } else {
                    params.encodings = [{}];
                }
                params.rtcp = {
                    compound: transceiver.rtcpParameters.compound
                };
                if (transceiver.rtcpParameters.cname) {
                    params.rtcp.cname = transceiver.rtcpParameters.cname;
                }
                if (transceiver.sendEncodingParameters.length) {
                    params.rtcp.ssrc = transceiver.sendEncodingParameters[0].ssrc;
                }
                transceiver.rtpReceiver.receive(params);
            }
        };

        RTCPeerConnection.prototype.setLocalDescription = function(description) {
            var pc = this;

            // Note: pranswer is not supported.
            if (['offer', 'answer'].indexOf(description.type) === -1) {
                return Promise.reject(makeError('TypeError',
                    'Unsupported type "' + description.type + '"'));
            }

            if (!isActionAllowedInSignalingState('setLocalDescription',
                    description.type, pc.signalingState) || pc._isClosed) {
                return Promise.reject(makeError('InvalidStateError',
                    'Can not set local ' + description.type +
                    ' in state ' + pc.signalingState));
            }

            var sections;
            var sessionpart;
            if (description.type === 'offer') {
                // VERY limited support for SDP munging. Limited to:
                // * changing the order of codecs
                sections = SDPUtils.splitSections(description.sdp);
                sessionpart = sections.shift();
                sections.forEach(function(mediaSection, sdpMLineIndex) {
                    var caps = SDPUtils.parseRtpParameters(mediaSection);
                    pc.transceivers[sdpMLineIndex].localCapabilities = caps;
                });

                pc.transceivers.forEach(function(transceiver, sdpMLineIndex) {
                    pc._gather(transceiver.mid, sdpMLineIndex);
                });
            } else if (description.type === 'answer') {
                sections = SDPUtils.splitSections(pc.remoteDescription.sdp);
                sessionpart = sections.shift();
                var isIceLite = SDPUtils.matchPrefix(sessionpart,
                        'a=ice-lite').length > 0;
                sections.forEach(function(mediaSection, sdpMLineIndex) {
                    var transceiver = pc.transceivers[sdpMLineIndex];
                    var iceGatherer = transceiver.iceGatherer;
                    var iceTransport = transceiver.iceTransport;
                    var dtlsTransport = transceiver.dtlsTransport;
                    var localCapabilities = transceiver.localCapabilities;
                    var remoteCapabilities = transceiver.remoteCapabilities;

                    // treat bundle-only as not-rejected.
                    var rejected = SDPUtils.isRejected(mediaSection) &&
                        SDPUtils.matchPrefix(mediaSection, 'a=bundle-only').length === 0;

                    if (!rejected && !transceiver.rejected) {
                        var remoteIceParameters = SDPUtils.getIceParameters(
                            mediaSection, sessionpart);
                        var remoteDtlsParameters = SDPUtils.getDtlsParameters(
                            mediaSection, sessionpart);
                        if (isIceLite) {
                            remoteDtlsParameters.role = 'server';
                        }

                        if (!pc.usingBundle || sdpMLineIndex === 0) {
                            pc._gather(transceiver.mid, sdpMLineIndex);
                            if (iceTransport.state === 'new') {
                                iceTransport.start(iceGatherer, remoteIceParameters,
                                    isIceLite ? 'controlling' : 'controlled');
                            }
                            if (dtlsTransport.state === 'new') {
                                dtlsTransport.start(remoteDtlsParameters);
                            }
                        }

                        // Calculate intersection of capabilities.
                        var params = getCommonCapabilities(localCapabilities,
                            remoteCapabilities);

                        // Start the RTCRtpSender. The RTCRtpReceiver for this
                        // transceiver has already been started in setRemoteDescription.
                        pc._transceive(transceiver,
                            params.codecs.length > 0,
                            false);
                    }
                });
            }

            pc.localDescription = {
                type: description.type,
                sdp: description.sdp
            };
            if (description.type === 'offer') {
                pc._updateSignalingState('have-local-offer');
            } else {
                pc._updateSignalingState('stable');
            }

            return Promise.resolve();
        };

        RTCPeerConnection.prototype.setRemoteDescription = function(description) {
            var pc = this;

            // Note: pranswer is not supported.
            if (['offer', 'answer'].indexOf(description.type) === -1) {
                return Promise.reject(makeError('TypeError',
                    'Unsupported type "' + description.type + '"'));
            }

            if (!isActionAllowedInSignalingState('setRemoteDescription',
                    description.type, pc.signalingState) || pc._isClosed) {
                return Promise.reject(makeError('InvalidStateError',
                    'Can not set remote ' + description.type +
                    ' in state ' + pc.signalingState));
            }

            var streams = {};
            pc.remoteStreams.forEach(function(stream) {
                streams[stream.id] = stream;
            });
            var receiverList = [];
            var sections = SDPUtils.splitSections(description.sdp);
            var sessionpart = sections.shift();
            var isIceLite = SDPUtils.matchPrefix(sessionpart,
                    'a=ice-lite').length > 0;
            var usingBundle = SDPUtils.matchPrefix(sessionpart,
                    'a=group:BUNDLE ').length > 0;
            pc.usingBundle = usingBundle;
            var iceOptions = SDPUtils.matchPrefix(sessionpart,
                'a=ice-options:')[0];
            if (iceOptions) {
                pc.canTrickleIceCandidates = iceOptions.substr(14).split(' ')
                        .indexOf('trickle') >= 0;
            } else {
                pc.canTrickleIceCandidates = false;
            }

            sections.forEach(function(mediaSection, sdpMLineIndex) {
                var lines = SDPUtils.splitLines(mediaSection);
                var kind = SDPUtils.getKind(mediaSection);
                // treat bundle-only as not-rejected.
                var rejected = SDPUtils.isRejected(mediaSection) &&
                    SDPUtils.matchPrefix(mediaSection, 'a=bundle-only').length === 0;
                var protocol = lines[0].substr(2).split(' ')[2];

                var direction = SDPUtils.getDirection(mediaSection, sessionpart);
                var remoteMsid = SDPUtils.parseMsid(mediaSection);

                var mid = SDPUtils.getMid(mediaSection) || SDPUtils.generateIdentifier();

                // Reject datachannels which are not implemented yet.
                if ((kind === 'application' && protocol === 'DTLS/SCTP') || rejected) {
                    // TODO: this is dangerous in the case where a non-rejected m-line
                    //     becomes rejected.
                    pc.transceivers[sdpMLineIndex] = {
                        mid: mid,
                        kind: kind,
                        rejected: true
                    };
                    return;
                }

                if (!rejected && pc.transceivers[sdpMLineIndex] &&
                    pc.transceivers[sdpMLineIndex].rejected) {
                    // recycle a rejected transceiver.
                    pc.transceivers[sdpMLineIndex] = pc._createTransceiver(kind, true);
                }

                var transceiver;
                var iceGatherer;
                var iceTransport;
                var dtlsTransport;
                var rtpReceiver;
                var sendEncodingParameters;
                var recvEncodingParameters;
                var localCapabilities;

                var track;
                // FIXME: ensure the mediaSection has rtcp-mux set.
                var remoteCapabilities = SDPUtils.parseRtpParameters(mediaSection);
                var remoteIceParameters;
                var remoteDtlsParameters;
                if (!rejected) {
                    remoteIceParameters = SDPUtils.getIceParameters(mediaSection,
                        sessionpart);
                    remoteDtlsParameters = SDPUtils.getDtlsParameters(mediaSection,
                        sessionpart);
                    remoteDtlsParameters.role = 'client';
                }
                recvEncodingParameters =
                    SDPUtils.parseRtpEncodingParameters(mediaSection);

                var rtcpParameters = SDPUtils.parseRtcpParameters(mediaSection);

                var isComplete = SDPUtils.matchPrefix(mediaSection,
                        'a=end-of-candidates', sessionpart).length > 0;
                var cands = SDPUtils.matchPrefix(mediaSection, 'a=candidate:')
                    .map(function(cand) {
                        return SDPUtils.parseCandidate(cand);
                    })
                    .filter(function(cand) {
                        return cand.component === 1;
                    });

                // Check if we can use BUNDLE and dispose transports.
                if ((description.type === 'offer' || description.type === 'answer') &&
                    !rejected && usingBundle && sdpMLineIndex > 0 &&
                    pc.transceivers[sdpMLineIndex]) {
                    pc._disposeIceAndDtlsTransports(sdpMLineIndex);
                    pc.transceivers[sdpMLineIndex].iceGatherer =
                        pc.transceivers[0].iceGatherer;
                    pc.transceivers[sdpMLineIndex].iceTransport =
                        pc.transceivers[0].iceTransport;
                    pc.transceivers[sdpMLineIndex].dtlsTransport =
                        pc.transceivers[0].dtlsTransport;
                    if (pc.transceivers[sdpMLineIndex].rtpSender) {
                        pc.transceivers[sdpMLineIndex].rtpSender.setTransport(
                            pc.transceivers[0].dtlsTransport);
                    }
                    if (pc.transceivers[sdpMLineIndex].rtpReceiver) {
                        pc.transceivers[sdpMLineIndex].rtpReceiver.setTransport(
                            pc.transceivers[0].dtlsTransport);
                    }
                }
                if (description.type === 'offer' && !rejected) {
                    transceiver = pc.transceivers[sdpMLineIndex] ||
                        pc._createTransceiver(kind);
                    transceiver.mid = mid;

                    if (!transceiver.iceGatherer) {
                        transceiver.iceGatherer = pc._createIceGatherer(sdpMLineIndex,
                            usingBundle);
                    }

                    if (cands.length && transceiver.iceTransport.state === 'new') {
                        if (isComplete && (!usingBundle || sdpMLineIndex === 0)) {
                            transceiver.iceTransport.setRemoteCandidates(cands);
                        } else {
                            cands.forEach(function(candidate) {
                                maybeAddCandidate(transceiver.iceTransport, candidate);
                            });
                        }
                    }

                    localCapabilities = window.RTCRtpReceiver.getCapabilities(kind);

                    // filter RTX until additional stuff needed for RTX is implemented
                    // in adapter.js
                    if (edgeVersion < 15019) {
                        localCapabilities.codecs = localCapabilities.codecs.filter(
                            function(codec) {
                                return codec.name !== 'rtx';
                            });
                    }

                    sendEncodingParameters = transceiver.sendEncodingParameters || [{
                            ssrc: (2 * sdpMLineIndex + 2) * 1001
                        }];

                    // TODO: rewrite to use http://w3c.github.io/webrtc-pc/#set-associated-remote-streams
                    var isNewTrack = false;
                    if (direction === 'sendrecv' || direction === 'sendonly') {
                        isNewTrack = !transceiver.rtpReceiver;
                        rtpReceiver = transceiver.rtpReceiver ||
                            new window.RTCRtpReceiver(transceiver.dtlsTransport, kind);

                        if (isNewTrack) {
                            var stream;
                            track = rtpReceiver.track;
                            // FIXME: does not work with Plan B.
                            if (remoteMsid && remoteMsid.stream === '-') {
                                // no-op. a stream id of '-' means: no associated stream.
                            } else if (remoteMsid) {
                                if (!streams[remoteMsid.stream]) {
                                    streams[remoteMsid.stream] = new window.MediaStream();
                                    Object.defineProperty(streams[remoteMsid.stream], 'id', {
                                        get: function() {
                                            return remoteMsid.stream;
                                        }
                                    });
                                }
                                Object.defineProperty(track, 'id', {
                                    get: function() {
                                        return remoteMsid.track;
                                    }
                                });
                                stream = streams[remoteMsid.stream];
                            } else {
                                if (!streams.default) {
                                    streams.default = new window.MediaStream();
                                }
                                stream = streams.default;
                            }
                            if (stream) {
                                addTrackToStreamAndFireEvent(track, stream);
                                transceiver.associatedRemoteMediaStreams.push(stream);
                            }
                            receiverList.push([track, rtpReceiver, stream]);
                        }
                    } else if (transceiver.rtpReceiver && transceiver.rtpReceiver.track) {
                        transceiver.associatedRemoteMediaStreams.forEach(function(s) {
                            var nativeTrack = s.getTracks().find(function(t) {
                                return t.id === transceiver.rtpReceiver.track.id;
                            });
                            if (nativeTrack) {
                                removeTrackFromStreamAndFireEvent(nativeTrack, s);
                            }
                        });
                        transceiver.associatedRemoteMediaStreams = [];
                    }

                    transceiver.localCapabilities = localCapabilities;
                    transceiver.remoteCapabilities = remoteCapabilities;
                    transceiver.rtpReceiver = rtpReceiver;
                    transceiver.rtcpParameters = rtcpParameters;
                    transceiver.sendEncodingParameters = sendEncodingParameters;
                    transceiver.recvEncodingParameters = recvEncodingParameters;

                    // Start the RTCRtpReceiver now. The RTPSender is started in
                    // setLocalDescription.
                    pc._transceive(pc.transceivers[sdpMLineIndex],
                        false,
                        isNewTrack);
                } else if (description.type === 'answer' && !rejected) {
                    transceiver = pc.transceivers[sdpMLineIndex];
                    iceGatherer = transceiver.iceGatherer;
                    iceTransport = transceiver.iceTransport;
                    dtlsTransport = transceiver.dtlsTransport;
                    rtpReceiver = transceiver.rtpReceiver;
                    sendEncodingParameters = transceiver.sendEncodingParameters;
                    localCapabilities = transceiver.localCapabilities;

                    pc.transceivers[sdpMLineIndex].recvEncodingParameters =
                        recvEncodingParameters;
                    pc.transceivers[sdpMLineIndex].remoteCapabilities =
                        remoteCapabilities;
                    pc.transceivers[sdpMLineIndex].rtcpParameters = rtcpParameters;

                    if (cands.length && iceTransport.state === 'new') {
                        if ((isIceLite || isComplete) &&
                            (!usingBundle || sdpMLineIndex === 0)) {
                            iceTransport.setRemoteCandidates(cands);
                        } else {
                            cands.forEach(function(candidate) {
                                maybeAddCandidate(transceiver.iceTransport, candidate);
                            });
                        }
                    }

                    if (!usingBundle || sdpMLineIndex === 0) {
                        if (iceTransport.state === 'new') {
                            iceTransport.start(iceGatherer, remoteIceParameters,
                                'controlling');
                        }
                        if (dtlsTransport.state === 'new') {
                            dtlsTransport.start(remoteDtlsParameters);
                        }
                    }

                    pc._transceive(transceiver,
                        direction === 'sendrecv' || direction === 'recvonly',
                        direction === 'sendrecv' || direction === 'sendonly');

                    // TODO: rewrite to use http://w3c.github.io/webrtc-pc/#set-associated-remote-streams
                    if (rtpReceiver &&
                        (direction === 'sendrecv' || direction === 'sendonly')) {
                        track = rtpReceiver.track;
                        if (remoteMsid) {
                            if (!streams[remoteMsid.stream]) {
                                streams[remoteMsid.stream] = new window.MediaStream();
                            }
                            addTrackToStreamAndFireEvent(track, streams[remoteMsid.stream]);
                            receiverList.push([track, rtpReceiver, streams[remoteMsid.stream]]);
                        } else {
                            if (!streams.default) {
                                streams.default = new window.MediaStream();
                            }
                            addTrackToStreamAndFireEvent(track, streams.default);
                            receiverList.push([track, rtpReceiver, streams.default]);
                        }
                    } else {
                        // FIXME: actually the receiver should be created later.
                        delete transceiver.rtpReceiver;
                    }
                }
            });

            if (pc._dtlsRole === undefined) {
                pc._dtlsRole = description.type === 'offer' ? 'active' : 'passive';
            }

            pc.remoteDescription = {
                type: description.type,
                sdp: description.sdp
            };
            if (description.type === 'offer') {
                pc._updateSignalingState('have-remote-offer');
            } else {
                pc._updateSignalingState('stable');
            }
            Object.keys(streams).forEach(function(sid) {
                var stream = streams[sid];
                if (stream.getTracks().length) {
                    if (pc.remoteStreams.indexOf(stream) === -1) {
                        pc.remoteStreams.push(stream);
                        var event = new Event('addstream');
                        event.stream = stream;
                        window.setTimeout(function() {
                            pc._dispatchEvent('addstream', event);
                        });
                    }

                    receiverList.forEach(function(item) {
                        var track = item[0];
                        var receiver = item[1];
                        if (stream.id !== item[2].id) {
                            return;
                        }
                        fireAddTrack(pc, track, receiver, [stream]);
                    });
                }
            });
            receiverList.forEach(function(item) {
                if (item[2]) {
                    return;
                }
                fireAddTrack(pc, item[0], item[1], []);
            });

            // check whether addIceCandidate({}) was called within four seconds after
            // setRemoteDescription.
            window.setTimeout(function() {
                if (!(pc && pc.transceivers)) {
                    return;
                }
                pc.transceivers.forEach(function(transceiver) {
                    if (transceiver.iceTransport &&
                        transceiver.iceTransport.state === 'new' &&
                        transceiver.iceTransport.getRemoteCandidates().length > 0) {
                        console.warn('Timeout for addRemoteCandidate. Consider sending ' +
                            'an end-of-candidates notification');
                        transceiver.iceTransport.addRemoteCandidate({});
                    }
                });
            }, 4000);

            return Promise.resolve();
        };

        RTCPeerConnection.prototype.close = function() {
            this.transceivers.forEach(function(transceiver) {
              /* not yet
               if (transceiver.iceGatherer) {
               transceiver.iceGatherer.close();
               }
               */
                if (transceiver.iceTransport) {
                    transceiver.iceTransport.stop();
                }
                if (transceiver.dtlsTransport) {
                    transceiver.dtlsTransport.stop();
                }
                if (transceiver.rtpSender) {
                    transceiver.rtpSender.stop();
                }
                if (transceiver.rtpReceiver) {
                    transceiver.rtpReceiver.stop();
                }
            });
            // FIXME: clean up tracks, local streams, remote streams, etc
            this._isClosed = true;
            this._updateSignalingState('closed');
        };

        // Update the signaling state.
        RTCPeerConnection.prototype._updateSignalingState = function(newState) {
            this.signalingState = newState;
            var event = new Event('signalingstatechange');
            this._dispatchEvent('signalingstatechange', event);
        };

        // Determine whether to fire the negotiationneeded event.
        RTCPeerConnection.prototype._maybeFireNegotiationNeeded = function() {
            var pc = this;
            if (this.signalingState !== 'stable' || this.needNegotiation === true) {
                return;
            }
            this.needNegotiation = true;
            window.setTimeout(function() {
                if (pc.needNegotiation) {
                    pc.needNegotiation = false;
                    var event = new Event('negotiationneeded');
                    pc._dispatchEvent('negotiationneeded', event);
                }
            }, 0);
        };

        // Update the ice connection state.
        RTCPeerConnection.prototype._updateIceConnectionState = function() {
            var newState;
            var states = {
                'new': 0,
                closed: 0,
                checking: 0,
                connected: 0,
                completed: 0,
                disconnected: 0,
                failed: 0
            };
            this.transceivers.forEach(function(transceiver) {
                states[transceiver.iceTransport.state]++;
            });

            newState = 'new';
            if (states.failed > 0) {
                newState = 'failed';
            } else if (states.checking > 0) {
                newState = 'checking';
            } else if (states.disconnected > 0) {
                newState = 'disconnected';
            } else if (states.new > 0) {
                newState = 'new';
            } else if (states.connected > 0) {
                newState = 'connected';
            } else if (states.completed > 0) {
                newState = 'completed';
            }

            if (newState !== this.iceConnectionState) {
                this.iceConnectionState = newState;
                var event = new Event('iceconnectionstatechange');
                this._dispatchEvent('iceconnectionstatechange', event);
            }
        };

        // Update the connection state.
        RTCPeerConnection.prototype._updateConnectionState = function() {
            var newState;
            var states = {
                'new': 0,
                closed: 0,
                connecting: 0,
                connected: 0,
                completed: 0,
                disconnected: 0,
                failed: 0
            };
            this.transceivers.forEach(function(transceiver) {
                states[transceiver.iceTransport.state]++;
                states[transceiver.dtlsTransport.state]++;
            });
            // ICETransport.completed and connected are the same for this purpose.
            states.connected += states.completed;

            newState = 'new';
            if (states.failed > 0) {
                newState = 'failed';
            } else if (states.connecting > 0) {
                newState = 'connecting';
            } else if (states.disconnected > 0) {
                newState = 'disconnected';
            } else if (states.new > 0) {
                newState = 'new';
            } else if (states.connected > 0) {
                newState = 'connected';
            }

            if (newState !== this.connectionState) {
                this.connectionState = newState;
                var event = new Event('connectionstatechange');
                this._dispatchEvent('connectionstatechange', event);
            }
        };

        RTCPeerConnection.prototype.createOffer = function() {
            var pc = this;

            if (pc._isClosed) {
                return Promise.reject(makeError('InvalidStateError',
                    'Can not call createOffer after close'));
            }

            var numAudioTracks = pc.transceivers.filter(function(t) {
                return t.kind === 'audio';
            }).length;
            var numVideoTracks = pc.transceivers.filter(function(t) {
                return t.kind === 'video';
            }).length;

            // Determine number of audio and video tracks we need to send/recv.
            var offerOptions = arguments[0];
            if (offerOptions) {
                // Reject Chrome legacy constraints.
                if (offerOptions.mandatory || offerOptions.optional) {
                    throw new TypeError(
                        'Legacy mandatory/optional constraints not supported.');
                }
                if (offerOptions.offerToReceiveAudio !== undefined) {
                    if (offerOptions.offerToReceiveAudio === true) {
                        numAudioTracks = 1;
                    } else if (offerOptions.offerToReceiveAudio === false) {
                        numAudioTracks = 0;
                    } else {
                        numAudioTracks = offerOptions.offerToReceiveAudio;
                    }
                }
                if (offerOptions.offerToReceiveVideo !== undefined) {
                    if (offerOptions.offerToReceiveVideo === true) {
                        numVideoTracks = 1;
                    } else if (offerOptions.offerToReceiveVideo === false) {
                        numVideoTracks = 0;
                    } else {
                        numVideoTracks = offerOptions.offerToReceiveVideo;
                    }
                }
            }

            pc.transceivers.forEach(function(transceiver) {
                if (transceiver.kind === 'audio') {
                    numAudioTracks--;
                    if (numAudioTracks < 0) {
                        transceiver.wantReceive = false;
                    }
                } else if (transceiver.kind === 'video') {
                    numVideoTracks--;
                    if (numVideoTracks < 0) {
                        transceiver.wantReceive = false;
                    }
                }
            });

            // Create M-lines for recvonly streams.
            while (numAudioTracks > 0 || numVideoTracks > 0) {
                if (numAudioTracks > 0) {
                    pc._createTransceiver('audio');
                    numAudioTracks--;
                }
                if (numVideoTracks > 0) {
                    pc._createTransceiver('video');
                    numVideoTracks--;
                }
            }

            var sdp = SDPUtils.writeSessionBoilerplate(pc._sdpSessionId,
                pc._sdpSessionVersion++);
            pc.transceivers.forEach(function(transceiver, sdpMLineIndex) {
                // For each track, create an ice gatherer, ice transport,
                // dtls transport, potentially rtpsender and rtpreceiver.
                var track = transceiver.track;
                var kind = transceiver.kind;
                var mid = transceiver.mid || SDPUtils.generateIdentifier();
                transceiver.mid = mid;

                if (!transceiver.iceGatherer) {
                    transceiver.iceGatherer = pc._createIceGatherer(sdpMLineIndex,
                        pc.usingBundle);
                }

                var localCapabilities = window.RTCRtpSender.getCapabilities(kind);
                // filter RTX until additional stuff needed for RTX is implemented
                // in adapter.js
                if (edgeVersion < 15019) {
                    localCapabilities.codecs = localCapabilities.codecs.filter(
                        function(codec) {
                            return codec.name !== 'rtx';
                        });
                }
                localCapabilities.codecs.forEach(function(codec) {
                    // work around https://bugs.chromium.org/p/webrtc/issues/detail?id=6552
                    // by adding level-asymmetry-allowed=1
                    if (codec.name === 'H264' &&
                        codec.parameters['level-asymmetry-allowed'] === undefined) {
                        codec.parameters['level-asymmetry-allowed'] = '1';
                    }

                    // for subsequent offers, we might have to re-use the payload
                    // type of the last offer.
                    if (transceiver.remoteCapabilities &&
                        transceiver.remoteCapabilities.codecs) {
                        transceiver.remoteCapabilities.codecs.forEach(function(remoteCodec) {
                            if (codec.name.toLowerCase() === remoteCodec.name.toLowerCase() &&
                                codec.clockRate === remoteCodec.clockRate) {
                                codec.preferredPayloadType = remoteCodec.payloadType;
                            }
                        });
                    }
                });
                localCapabilities.headerExtensions.forEach(function(hdrExt) {
                    var remoteExtensions = transceiver.remoteCapabilities &&
                        transceiver.remoteCapabilities.headerExtensions || [];
                    remoteExtensions.forEach(function(rHdrExt) {
                        if (hdrExt.uri === rHdrExt.uri) {
                            hdrExt.id = rHdrExt.id;
                        }
                    });
                });

                // generate an ssrc now, to be used later in rtpSender.send
                var sendEncodingParameters = transceiver.sendEncodingParameters || [{
                        ssrc: (2 * sdpMLineIndex + 1) * 1001
                    }];
                if (track) {
                    // add RTX
                    if (edgeVersion >= 15019 && kind === 'video' &&
                        !sendEncodingParameters[0].rtx) {
                        sendEncodingParameters[0].rtx = {
                            ssrc: sendEncodingParameters[0].ssrc + 1
                        };
                    }
                }

                if (transceiver.wantReceive) {
                    transceiver.rtpReceiver = new window.RTCRtpReceiver(
                        transceiver.dtlsTransport, kind);
                }

                transceiver.localCapabilities = localCapabilities;
                transceiver.sendEncodingParameters = sendEncodingParameters;
            });

            // always offer BUNDLE and dispose on return if not supported.
            if (pc._config.bundlePolicy !== 'max-compat') {
                sdp += 'a=group:BUNDLE ' + pc.transceivers.map(function(t) {
                        return t.mid;
                    }).join(' ') + '\r\n';
            }
            sdp += 'a=ice-options:trickle\r\n';

            pc.transceivers.forEach(function(transceiver, sdpMLineIndex) {
                sdp += writeMediaSection(transceiver, transceiver.localCapabilities,
                    'offer', transceiver.stream, pc._dtlsRole);
                sdp += 'a=rtcp-rsize\r\n';

                if (transceiver.iceGatherer && pc.iceGatheringState !== 'new' &&
                    (sdpMLineIndex === 0 || !pc.usingBundle)) {
                    transceiver.iceGatherer.getLocalCandidates().forEach(function(cand) {
                        cand.component = 1;
                        sdp += 'a=' + SDPUtils.writeCandidate(cand) + '\r\n';
                    });

                    if (transceiver.iceGatherer.state === 'completed') {
                        sdp += 'a=end-of-candidates\r\n';
                    }
                }
            });

            var desc = new window.RTCSessionDescription({
                type: 'offer',
                sdp: sdp
            });
            return Promise.resolve(desc);
        };

        RTCPeerConnection.prototype.createAnswer = function() {
            var pc = this;

            if (pc._isClosed) {
                return Promise.reject(makeError('InvalidStateError',
                    'Can not call createAnswer after close'));
            }

            if (!(pc.signalingState === 'have-remote-offer' ||
                pc.signalingState === 'have-local-pranswer')) {
                return Promise.reject(makeError('InvalidStateError',
                    'Can not call createAnswer in signalingState ' + pc.signalingState));
            }

            var sdp = SDPUtils.writeSessionBoilerplate(pc._sdpSessionId,
                pc._sdpSessionVersion++);
            if (pc.usingBundle) {
                sdp += 'a=group:BUNDLE ' + pc.transceivers.map(function(t) {
                        return t.mid;
                    }).join(' ') + '\r\n';
            }
            var mediaSectionsInOffer = SDPUtils.getMediaSections(
                pc.remoteDescription.sdp).length;
            pc.transceivers.forEach(function(transceiver, sdpMLineIndex) {
                if (sdpMLineIndex + 1 > mediaSectionsInOffer) {
                    return;
                }
                if (transceiver.rejected) {
                    if (transceiver.kind === 'application') {
                        sdp += 'm=application 0 DTLS/SCTP 5000\r\n';
                    } else if (transceiver.kind === 'audio') {
                        sdp += 'm=audio 0 UDP/TLS/RTP/SAVPF 0\r\n' +
                            'a=rtpmap:0 PCMU/8000\r\n';
                    } else if (transceiver.kind === 'video') {
                        sdp += 'm=video 0 UDP/TLS/RTP/SAVPF 120\r\n' +
                            'a=rtpmap:120 VP8/90000\r\n';
                    }
                    sdp += 'c=IN IP4 0.0.0.0\r\n' +
                        'a=inactive\r\n' +
                        'a=mid:' + transceiver.mid + '\r\n';
                    return;
                }

                // FIXME: look at direction.
                if (transceiver.stream) {
                    var localTrack;
                    if (transceiver.kind === 'audio') {
                        localTrack = transceiver.stream.getAudioTracks()[0];
                    } else if (transceiver.kind === 'video') {
                        localTrack = transceiver.stream.getVideoTracks()[0];
                    }
                    if (localTrack) {
                        // add RTX
                        if (edgeVersion >= 15019 && transceiver.kind === 'video' &&
                            !transceiver.sendEncodingParameters[0].rtx) {
                            transceiver.sendEncodingParameters[0].rtx = {
                                ssrc: transceiver.sendEncodingParameters[0].ssrc + 1
                            };
                        }
                    }
                }

                // Calculate intersection of capabilities.
                var commonCapabilities = getCommonCapabilities(
                    transceiver.localCapabilities,
                    transceiver.remoteCapabilities);

                var hasRtx = commonCapabilities.codecs.filter(function(c) {
                    return c.name.toLowerCase() === 'rtx';
                }).length;
                if (!hasRtx && transceiver.sendEncodingParameters[0].rtx) {
                    delete transceiver.sendEncodingParameters[0].rtx;
                }

                sdp += writeMediaSection(transceiver, commonCapabilities,
                    'answer', transceiver.stream, pc._dtlsRole);
                if (transceiver.rtcpParameters &&
                    transceiver.rtcpParameters.reducedSize) {
                    sdp += 'a=rtcp-rsize\r\n';
                }
            });

            var desc = new window.RTCSessionDescription({
                type: 'answer',
                sdp: sdp
            });
            return Promise.resolve(desc);
        };

        RTCPeerConnection.prototype.addIceCandidate = function(candidate) {
            var pc = this;
            var sections;
            if (candidate && !(candidate.sdpMLineIndex !== undefined ||
                candidate.sdpMid)) {
                return Promise.reject(new TypeError('sdpMLineIndex or sdpMid required'));
            }

            // TODO: needs to go into ops queue.
            return new Promise(function(resolve, reject) {
                if (!pc.remoteDescription) {
                    return reject(makeError('InvalidStateError',
                        'Can not add ICE candidate without a remote description'));
                } else if (!candidate || candidate.candidate === '') {
                    for (var j = 0; j < pc.transceivers.length; j++) {
                        if (pc.transceivers[j].rejected) {
                            continue;
                        }
                        pc.transceivers[j].iceTransport.addRemoteCandidate({});
                        sections = SDPUtils.getMediaSections(pc.remoteDescription.sdp);
                        sections[j] += 'a=end-of-candidates\r\n';
                        pc.remoteDescription.sdp =
                            SDPUtils.getDescription(pc.remoteDescription.sdp) +
                            sections.join('');
                        if (pc.usingBundle) {
                            break;
                        }
                    }
                } else {
                    var sdpMLineIndex = candidate.sdpMLineIndex;
                    if (candidate.sdpMid) {
                        for (var i = 0; i < pc.transceivers.length; i++) {
                            if (pc.transceivers[i].mid === candidate.sdpMid) {
                                sdpMLineIndex = i;
                                break;
                            }
                        }
                    }
                    var transceiver = pc.transceivers[sdpMLineIndex];
                    if (transceiver) {
                        if (transceiver.rejected) {
                            return resolve();
                        }
                        var cand = Object.keys(candidate.candidate).length > 0 ?
                            SDPUtils.parseCandidate(candidate.candidate) : {};
                        // Ignore Chrome's invalid candidates since Edge does not like them.
                        if (cand.protocol === 'tcp' && (cand.port === 0 || cand.port === 9)) {
                            return resolve();
                        }
                        // Ignore RTCP candidates, we assume RTCP-MUX.
                        if (cand.component && cand.component !== 1) {
                            return resolve();
                        }
                        // when using bundle, avoid adding candidates to the wrong
                        // ice transport. And avoid adding candidates added in the SDP.
                        if (sdpMLineIndex === 0 || (sdpMLineIndex > 0 &&
                            transceiver.iceTransport !== pc.transceivers[0].iceTransport)) {
                            if (!maybeAddCandidate(transceiver.iceTransport, cand)) {
                                return reject(makeError('OperationError',
                                    'Can not add ICE candidate'));
                            }
                        }

                        // update the remoteDescription.
                        var candidateString = candidate.candidate.trim();
                        if (candidateString.indexOf('a=') === 0) {
                            candidateString = candidateString.substr(2);
                        }
                        sections = SDPUtils.getMediaSections(pc.remoteDescription.sdp);
                        sections[sdpMLineIndex] += 'a=' +
                            (cand.type ? candidateString : 'end-of-candidates')
                            + '\r\n';
                        pc.remoteDescription.sdp =
                            SDPUtils.getDescription(pc.remoteDescription.sdp) +
                            sections.join('');
                    } else {
                        return reject(makeError('OperationError',
                            'Can not add ICE candidate'));
                    }
                }
                resolve();
            });
        };

        RTCPeerConnection.prototype.getStats = function(selector) {
            if (selector && selector instanceof window.MediaStreamTrack) {
                var senderOrReceiver = null;
                this.transceivers.forEach(function(transceiver) {
                    if (transceiver.rtpSender &&
                        transceiver.rtpSender.track === selector) {
                        senderOrReceiver = transceiver.rtpSender;
                    } else if (transceiver.rtpReceiver &&
                        transceiver.rtpReceiver.track === selector) {
                        senderOrReceiver = transceiver.rtpReceiver;
                    }
                });
                if (!senderOrReceiver) {
                    throw makeError('InvalidAccessError', 'Invalid selector.');
                }
                return senderOrReceiver.getStats();
            }

            var promises = [];
            this.transceivers.forEach(function(transceiver) {
                ['rtpSender', 'rtpReceiver', 'iceGatherer', 'iceTransport',
                    'dtlsTransport'].forEach(function(method) {
                    if (transceiver[method]) {
                        promises.push(transceiver[method].getStats());
                    }
                });
            });
            return Promise.all(promises).then(function(allStats) {
                var results = new Map();
                allStats.forEach(function(stats) {
                    stats.forEach(function(stat) {
                        results.set(stat.id, stat);
                    });
                });
                return results;
            });
        };

        // fix low-level stat names and return Map instead of object.
        var ortcObjects = ['RTCRtpSender', 'RTCRtpReceiver', 'RTCIceGatherer',
            'RTCIceTransport', 'RTCDtlsTransport'];
        ortcObjects.forEach(function(ortcObjectName) {
            var obj = window[ortcObjectName];
            if (obj && obj.prototype && obj.prototype.getStats) {
                var nativeGetstats = obj.prototype.getStats;
                obj.prototype.getStats = function() {
                    return nativeGetstats.apply(this)
                        .then(function(nativeStats) {
                            var mapStats = new Map();
                            Object.keys(nativeStats).forEach(function(id) {
                                nativeStats[id].type = fixStatsType(nativeStats[id]);
                                mapStats.set(id, nativeStats[id]);
                            });
                            return mapStats;
                        });
                };
            }
        });

        // legacy callback shims. Should be moved to adapter.js some days.
        var methods = ['createOffer', 'createAnswer'];
        methods.forEach(function(method) {
            var nativeMethod = RTCPeerConnection.prototype[method];
            RTCPeerConnection.prototype[method] = function() {
                var args = arguments;
                if (typeof args[0] === 'function' ||
                    typeof args[1] === 'function') { // legacy
                    return nativeMethod.apply(this, [arguments[2]])
                        .then(function(description) {
                            if (typeof args[0] === 'function') {
                                args[0].apply(null, [description]);
                            }
                        }, function(error) {
                            if (typeof args[1] === 'function') {
                                args[1].apply(null, [error]);
                            }
                        });
                }
                return nativeMethod.apply(this, arguments);
            };
        });

        methods = ['setLocalDescription', 'setRemoteDescription', 'addIceCandidate'];
        methods.forEach(function(method) {
            var nativeMethod = RTCPeerConnection.prototype[method];
            RTCPeerConnection.prototype[method] = function() {
                var args = arguments;
                if (typeof args[1] === 'function' ||
                    typeof args[2] === 'function') { // legacy
                    return nativeMethod.apply(this, arguments)
                        .then(function() {
                            if (typeof args[1] === 'function') {
                                args[1].apply(null);
                            }
                        }, function(error) {
                            if (typeof args[2] === 'function') {
                                args[2].apply(null, [error]);
                            }
                        });
                }
                return nativeMethod.apply(this, arguments);
            };
        });

        // getStats is special. It doesn't have a spec legacy method yet we support
        // getStats(something, cb) without error callbacks.
        ['getStats'].forEach(function(method) {
            var nativeMethod = RTCPeerConnection.prototype[method];
            RTCPeerConnection.prototype[method] = function() {
                var args = arguments;
                if (typeof args[1] === 'function') {
                    return nativeMethod.apply(this, arguments)
                        .then(function() {
                            if (typeof args[1] === 'function') {
                                args[1].apply(null);
                            }
                        });
                }
                return nativeMethod.apply(this, arguments);
            };
        });

        return RTCPeerConnection;
    };

},{"sdp":2}],2:[function(require,module,exports){
  /* eslint-env node */
    'use strict';

// SDP helpers.
    var SDPUtils = {};

// Generate an alphanumeric identifier for cname or mids.
// TODO: use UUIDs instead? https://gist.github.com/jed/982883
    SDPUtils.generateIdentifier = function() {
        return Math.random().toString(36).substr(2, 10);
    };

// The RTCP CNAME used by all peerconnections from the same JS.
    SDPUtils.localCName = SDPUtils.generateIdentifier();

// Splits SDP into lines, dealing with both CRLF and LF.
    SDPUtils.splitLines = function(blob) {
        return blob.trim().split('\n').map(function(line) {
            return line.trim();
        });
    };
// Splits SDP into sessionpart and mediasections. Ensures CRLF.
    SDPUtils.splitSections = function(blob) {
        var parts = blob.split('\nm=');
        return parts.map(function(part, index) {
            return (index > 0 ? 'm=' + part : part).trim() + '\r\n';
        });
    };

// returns the session description.
    SDPUtils.getDescription = function(blob) {
        var sections = SDPUtils.splitSections(blob);
        return sections && sections[0];
    };

// returns the individual media sections.
    SDPUtils.getMediaSections = function(blob) {
        var sections = SDPUtils.splitSections(blob);
        sections.shift();
        return sections;
    };

// Returns lines that start with a certain prefix.
    SDPUtils.matchPrefix = function(blob, prefix) {
        return SDPUtils.splitLines(blob).filter(function(line) {
            return line.indexOf(prefix) === 0;
        });
    };

// Parses an ICE candidate line. Sample input:
// candidate:702786350 2 udp 41819902 8.8.8.8 60769 typ relay raddr 8.8.8.8
// rport 55996"
    SDPUtils.parseCandidate = function(line) {
        var parts;
        // Parse both variants.
        if (line.indexOf('a=candidate:') === 0) {
            parts = line.substring(12).split(' ');
        } else {
            parts = line.substring(10).split(' ');
        }

        var candidate = {
            foundation: parts[0],
            component: parseInt(parts[1], 10),
            protocol: parts[2].toLowerCase(),
            priority: parseInt(parts[3], 10),
            ip: parts[4],
            port: parseInt(parts[5], 10),
            // skip parts[6] == 'typ'
            type: parts[7]
        };

        for (var i = 8; i < parts.length; i += 2) {
            switch (parts[i]) {
                case 'raddr':
                    candidate.relatedAddress = parts[i + 1];
                    break;
                case 'rport':
                    candidate.relatedPort = parseInt(parts[i + 1], 10);
                    break;
                case 'tcptype':
                    candidate.tcpType = parts[i + 1];
                    break;
                case 'ufrag':
                    candidate.ufrag = parts[i + 1]; // for backward compability.
                    candidate.usernameFragment = parts[i + 1];
                    break;
                default: // extension handling, in particular ufrag
                    candidate[parts[i]] = parts[i + 1];
                    break;
            }
        }
        return candidate;
    };

// Translates a candidate object into SDP candidate attribute.
    SDPUtils.writeCandidate = function(candidate) {
        var sdp = [];
        sdp.push(candidate.foundation);
        sdp.push(candidate.component);
        sdp.push(candidate.protocol.toUpperCase());
        sdp.push(candidate.priority);
        sdp.push(candidate.ip);
        sdp.push(candidate.port);

        var type = candidate.type;
        sdp.push('typ');
        sdp.push(type);
        if (type !== 'host' && candidate.relatedAddress &&
            candidate.relatedPort) {
            sdp.push('raddr');
            sdp.push(candidate.relatedAddress);
            sdp.push('rport');
            sdp.push(candidate.relatedPort);
        }
        if (candidate.tcpType && candidate.protocol.toLowerCase() === 'tcp') {
            sdp.push('tcptype');
            sdp.push(candidate.tcpType);
        }
        if (candidate.usernameFragment || candidate.ufrag) {
            sdp.push('ufrag');
            sdp.push(candidate.usernameFragment || candidate.ufrag);
        }
        return 'candidate:' + sdp.join(' ');
    };

// Parses an ice-options line, returns an array of option tags.
// a=ice-options:foo bar
    SDPUtils.parseIceOptions = function(line) {
        return line.substr(14).split(' ');
    }

// Parses an rtpmap line, returns RTCRtpCoddecParameters. Sample input:
// a=rtpmap:111 opus/48000/2
    SDPUtils.parseRtpMap = function(line) {
        var parts = line.substr(9).split(' ');
        var parsed = {
            payloadType: parseInt(parts.shift(), 10) // was: id
        };

        parts = parts[0].split('/');

        parsed.name = parts[0];
        parsed.clockRate = parseInt(parts[1], 10); // was: clockrate
        parsed.channels = parts.length === 3 ? parseInt(parts[2], 10) : 1;
        // legacy alias, got renamed back to channels in ORTC.
        parsed.numChannels = parsed.channels;
        return parsed;
    };

// Generate an a=rtpmap line from RTCRtpCodecCapability or
// RTCRtpCodecParameters.
    SDPUtils.writeRtpMap = function(codec) {
        var pt = codec.payloadType;
        if (codec.preferredPayloadType !== undefined) {
            pt = codec.preferredPayloadType;
        }
        var channels = codec.channels || codec.numChannels || 1;
        return 'a=rtpmap:' + pt + ' ' + codec.name + '/' + codec.clockRate +
            (channels !== 1 ? '/' + channels : '') + '\r\n';
    };

// Parses an a=extmap line (headerextension from RFC 5285). Sample input:
// a=extmap:2 urn:ietf:params:rtp-hdrext:toffset
// a=extmap:2/sendonly urn:ietf:params:rtp-hdrext:toffset
    SDPUtils.parseExtmap = function(line) {
        var parts = line.substr(9).split(' ');
        return {
            id: parseInt(parts[0], 10),
            direction: parts[0].indexOf('/') > 0 ? parts[0].split('/')[1] : 'sendrecv',
            uri: parts[1]
        };
    };

// Generates a=extmap line from RTCRtpHeaderExtensionParameters or
// RTCRtpHeaderExtension.
    SDPUtils.writeExtmap = function(headerExtension) {
        return 'a=extmap:' + (headerExtension.id || headerExtension.preferredId) +
            (headerExtension.direction && headerExtension.direction !== 'sendrecv'
                ? '/' + headerExtension.direction
                : '') +
            ' ' + headerExtension.uri + '\r\n';
    };

// Parses an ftmp line, returns dictionary. Sample input:
// a=fmtp:96 vbr=on;cng=on
// Also deals with vbr=on; cng=on
    SDPUtils.parseFmtp = function(line) {
        var parsed = {};
        var kv;
        var parts = line.substr(line.indexOf(' ') + 1).split(';');
        for (var j = 0; j < parts.length; j++) {
            kv = parts[j].trim().split('=');
            parsed[kv[0].trim()] = kv[1];
        }
        return parsed;
    };

// Generates an a=ftmp line from RTCRtpCodecCapability or RTCRtpCodecParameters.
    SDPUtils.writeFmtp = function(codec) {
        var line = '';
        var pt = codec.payloadType;
        if (codec.preferredPayloadType !== undefined) {
            pt = codec.preferredPayloadType;
        }
        if (codec.parameters && Object.keys(codec.parameters).length) {
            var params = [];
            Object.keys(codec.parameters).forEach(function(param) {
                if (codec.parameters[param]) {
                    params.push(param + '=' + codec.parameters[param]);
                } else {
                    params.push(param);
                }
            });
            line += 'a=fmtp:' + pt + ' ' + params.join(';') + '\r\n';
        }
        return line;
    };

// Parses an rtcp-fb line, returns RTCPRtcpFeedback object. Sample input:
// a=rtcp-fb:98 nack rpsi
    SDPUtils.parseRtcpFb = function(line) {
        var parts = line.substr(line.indexOf(' ') + 1).split(' ');
        return {
            type: parts.shift(),
            parameter: parts.join(' ')
        };
    };
// Generate a=rtcp-fb lines from RTCRtpCodecCapability or RTCRtpCodecParameters.
    SDPUtils.writeRtcpFb = function(codec) {
        var lines = '';
        var pt = codec.payloadType;
        if (codec.preferredPayloadType !== undefined) {
            pt = codec.preferredPayloadType;
        }
        if (codec.rtcpFeedback && codec.rtcpFeedback.length) {
            // FIXME: special handling for trr-int?
            codec.rtcpFeedback.forEach(function(fb) {
                lines += 'a=rtcp-fb:' + pt + ' ' + fb.type +
                    (fb.parameter && fb.parameter.length ? ' ' + fb.parameter : '') +
                    '\r\n';
            });
        }
        return lines;
    };

// Parses an RFC 5576 ssrc media attribute. Sample input:
// a=ssrc:3735928559 cname:something
    SDPUtils.parseSsrcMedia = function(line) {
        var sp = line.indexOf(' ');
        var parts = {
            ssrc: parseInt(line.substr(7, sp - 7), 10)
        };
        var colon = line.indexOf(':', sp);
        if (colon > -1) {
            parts.attribute = line.substr(sp + 1, colon - sp - 1);
            parts.value = line.substr(colon + 1);
        } else {
            parts.attribute = line.substr(sp + 1);
        }
        return parts;
    };

// Extracts the MID (RFC 5888) from a media section.
// returns the MID or undefined if no mid line was found.
    SDPUtils.getMid = function(mediaSection) {
        var mid = SDPUtils.matchPrefix(mediaSection, 'a=mid:')[0];
        if (mid) {
            return mid.substr(6);
        }
    }

    SDPUtils.parseFingerprint = function(line) {
        var parts = line.substr(14).split(' ');
        return {
            algorithm: parts[0].toLowerCase(), // algorithm is case-sensitive in Edge.
            value: parts[1]
        };
    };

// Extracts DTLS parameters from SDP media section or sessionpart.
// FIXME: for consistency with other functions this should only
//   get the fingerprint line as input. See also getIceParameters.
    SDPUtils.getDtlsParameters = function(mediaSection, sessionpart) {
        var lines = SDPUtils.matchPrefix(mediaSection + sessionpart,
            'a=fingerprint:');
        // Note: a=setup line is ignored since we use the 'auto' role.
        // Note2: 'algorithm' is not case sensitive except in Edge.
        return {
            role: 'auto',
            fingerprints: lines.map(SDPUtils.parseFingerprint)
        };
    };

// Serializes DTLS parameters to SDP.
    SDPUtils.writeDtlsParameters = function(params, setupType) {
        var sdp = 'a=setup:' + setupType + '\r\n';
        params.fingerprints.forEach(function(fp) {
            sdp += 'a=fingerprint:' + fp.algorithm + ' ' + fp.value + '\r\n';
        });
        return sdp;
    };
// Parses ICE information from SDP media section or sessionpart.
// FIXME: for consistency with other functions this should only
//   get the ice-ufrag and ice-pwd lines as input.
    SDPUtils.getIceParameters = function(mediaSection, sessionpart) {
        var lines = SDPUtils.splitLines(mediaSection);
        // Search in session part, too.
        lines = lines.concat(SDPUtils.splitLines(sessionpart));
        var iceParameters = {
            usernameFragment: lines.filter(function(line) {
                return line.indexOf('a=ice-ufrag:') === 0;
            })[0].substr(12),
            password: lines.filter(function(line) {
                return line.indexOf('a=ice-pwd:') === 0;
            })[0].substr(10)
        };
        return iceParameters;
    };

// Serializes ICE parameters to SDP.
    SDPUtils.writeIceParameters = function(params) {
        return 'a=ice-ufrag:' + params.usernameFragment + '\r\n' +
            'a=ice-pwd:' + params.password + '\r\n';
    };

// Parses the SDP media section and returns RTCRtpParameters.
    SDPUtils.parseRtpParameters = function(mediaSection) {
        var description = {
            codecs: [],
            headerExtensions: [],
            fecMechanisms: [],
            rtcp: []
        };
        var lines = SDPUtils.splitLines(mediaSection);
        var mline = lines[0].split(' ');
        for (var i = 3; i < mline.length; i++) { // find all codecs from mline[3..]
            var pt = mline[i];
            var rtpmapline = SDPUtils.matchPrefix(
                mediaSection, 'a=rtpmap:' + pt + ' ')[0];
            if (rtpmapline) {
                var codec = SDPUtils.parseRtpMap(rtpmapline);
                var fmtps = SDPUtils.matchPrefix(
                    mediaSection, 'a=fmtp:' + pt + ' ');
                // Only the first a=fmtp:<pt> is considered.
                codec.parameters = fmtps.length ? SDPUtils.parseFmtp(fmtps[0]) : {};
                codec.rtcpFeedback = SDPUtils.matchPrefix(
                    mediaSection, 'a=rtcp-fb:' + pt + ' ')
                    .map(SDPUtils.parseRtcpFb);
                description.codecs.push(codec);
                // parse FEC mechanisms from rtpmap lines.
                switch (codec.name.toUpperCase()) {
                    case 'RED':
                    case 'ULPFEC':
                        description.fecMechanisms.push(codec.name.toUpperCase());
                        break;
                    default: // only RED and ULPFEC are recognized as FEC mechanisms.
                        break;
                }
            }
        }
        SDPUtils.matchPrefix(mediaSection, 'a=extmap:').forEach(function(line) {
            description.headerExtensions.push(SDPUtils.parseExtmap(line));
        });
        // FIXME: parse rtcp.
        return description;
    };

// Generates parts of the SDP media section describing the capabilities /
// parameters.
    SDPUtils.writeRtpDescription = function(kind, caps) {
        var sdp = '';

        // Build the mline.
        sdp += 'm=' + kind + ' ';
        sdp += caps.codecs.length > 0 ? '9' : '0'; // reject if no codecs.
        sdp += ' UDP/TLS/RTP/SAVPF ';
        sdp += caps.codecs.map(function(codec) {
                if (codec.preferredPayloadType !== undefined) {
                    return codec.preferredPayloadType;
                }
                return codec.payloadType;
            }).join(' ') + '\r\n';

        sdp += 'c=IN IP4 0.0.0.0\r\n';
        sdp += 'a=rtcp:9 IN IP4 0.0.0.0\r\n';

        // Add a=rtpmap lines for each codec. Also fmtp and rtcp-fb.
        caps.codecs.forEach(function(codec) {
            sdp += SDPUtils.writeRtpMap(codec);
            sdp += SDPUtils.writeFmtp(codec);
            sdp += SDPUtils.writeRtcpFb(codec);
        });
        var maxptime = 0;
        caps.codecs.forEach(function(codec) {
            if (codec.maxptime > maxptime) {
                maxptime = codec.maxptime;
            }
        });
        if (maxptime > 0) {
            sdp += 'a=maxptime:' + maxptime + '\r\n';
        }
        sdp += 'a=rtcp-mux\r\n';

        if (caps.headerExtensions) {
            caps.headerExtensions.forEach(function(extension) {
                sdp += SDPUtils.writeExtmap(extension);
            });
        }
        // FIXME: write fecMechanisms.
        return sdp;
    };

// Parses the SDP media section and returns an array of
// RTCRtpEncodingParameters.
    SDPUtils.parseRtpEncodingParameters = function(mediaSection) {
        var encodingParameters = [];
        var description = SDPUtils.parseRtpParameters(mediaSection);
        var hasRed = description.fecMechanisms.indexOf('RED') !== -1;
        var hasUlpfec = description.fecMechanisms.indexOf('ULPFEC') !== -1;

        // filter a=ssrc:... cname:, ignore PlanB-msid
        var ssrcs = SDPUtils.matchPrefix(mediaSection, 'a=ssrc:')
            .map(function(line) {
                return SDPUtils.parseSsrcMedia(line);
            })
            .filter(function(parts) {
                return parts.attribute === 'cname';
            });
        var primarySsrc = ssrcs.length > 0 && ssrcs[0].ssrc;
        var secondarySsrc;

        var flows = SDPUtils.matchPrefix(mediaSection, 'a=ssrc-group:FID')
            .map(function(line) {
                var parts = line.substr(17).split(' ');
                return parts.map(function(part) {
                    return parseInt(part, 10);
                });
            });
        if (flows.length > 0 && flows[0].length > 1 && flows[0][0] === primarySsrc) {
            secondarySsrc = flows[0][1];
        }

        description.codecs.forEach(function(codec) {
            if (codec.name.toUpperCase() === 'RTX' && codec.parameters.apt) {
                var encParam = {
                    ssrc: primarySsrc,
                    codecPayloadType: parseInt(codec.parameters.apt, 10),
                };
                if (primarySsrc && secondarySsrc) {
                    encParam.rtx = {ssrc: secondarySsrc};
                }
                encodingParameters.push(encParam);
                if (hasRed) {
                    encParam = JSON.parse(JSON.stringify(encParam));
                    encParam.fec = {
                        ssrc: secondarySsrc,
                        mechanism: hasUlpfec ? 'red+ulpfec' : 'red'
                    };
                    encodingParameters.push(encParam);
                }
            }
        });
        if (encodingParameters.length === 0 && primarySsrc) {
            encodingParameters.push({
                ssrc: primarySsrc
            });
        }

        // we support both b=AS and b=TIAS but interpret AS as TIAS.
        var bandwidth = SDPUtils.matchPrefix(mediaSection, 'b=');
        if (bandwidth.length) {
            if (bandwidth[0].indexOf('b=TIAS:') === 0) {
                bandwidth = parseInt(bandwidth[0].substr(7), 10);
            } else if (bandwidth[0].indexOf('b=AS:') === 0) {
                // use formula from JSEP to convert b=AS to TIAS value.
                bandwidth = parseInt(bandwidth[0].substr(5), 10) * 1000 * 0.95
                    - (50 * 40 * 8);
            } else {
                bandwidth = undefined;
            }
            encodingParameters.forEach(function(params) {
                params.maxBitrate = bandwidth;
            });
        }
        return encodingParameters;
    };

// parses http://draft.ortc.org/#rtcrtcpparameters*
    SDPUtils.parseRtcpParameters = function(mediaSection) {
        var rtcpParameters = {};

        var cname;
        // Gets the first SSRC. Note that with RTX there might be multiple
        // SSRCs.
        var remoteSsrc = SDPUtils.matchPrefix(mediaSection, 'a=ssrc:')
            .map(function(line) {
                return SDPUtils.parseSsrcMedia(line);
            })
            .filter(function(obj) {
                return obj.attribute === 'cname';
            })[0];
        if (remoteSsrc) {
            rtcpParameters.cname = remoteSsrc.value;
            rtcpParameters.ssrc = remoteSsrc.ssrc;
        }

        // Edge uses the compound attribute instead of reducedSize
        // compound is !reducedSize
        var rsize = SDPUtils.matchPrefix(mediaSection, 'a=rtcp-rsize');
        rtcpParameters.reducedSize = rsize.length > 0;
        rtcpParameters.compound = rsize.length === 0;

        // parses the rtcp-mux attrіbute.
        // Note that Edge does not support unmuxed RTCP.
        var mux = SDPUtils.matchPrefix(mediaSection, 'a=rtcp-mux');
        rtcpParameters.mux = mux.length > 0;

        return rtcpParameters;
    };

// parses either a=msid: or a=ssrc:... msid lines and returns
// the id of the MediaStream and MediaStreamTrack.
    SDPUtils.parseMsid = function(mediaSection) {
        var parts;
        var spec = SDPUtils.matchPrefix(mediaSection, 'a=msid:');
        if (spec.length === 1) {
            parts = spec[0].substr(7).split(' ');
            return {stream: parts[0], track: parts[1]};
        }
        var planB = SDPUtils.matchPrefix(mediaSection, 'a=ssrc:')
            .map(function(line) {
                return SDPUtils.parseSsrcMedia(line);
            })
            .filter(function(parts) {
                return parts.attribute === 'msid';
            });
        if (planB.length > 0) {
            parts = planB[0].value.split(' ');
            return {stream: parts[0], track: parts[1]};
        }
    };

// Generate a session ID for SDP.
// https://tools.ietf.org/html/draft-ietf-rtcweb-jsep-20#section-5.2.1
// recommends using a cryptographically random +ve 64-bit value
// but right now this should be acceptable and within the right range
    SDPUtils.generateSessionId = function() {
        return Math.random().toString().substr(2, 21);
    };

// Write boilder plate for start of SDP
// sessId argument is optional - if not supplied it will
// be generated randomly
// sessVersion is optional and defaults to 2
    SDPUtils.writeSessionBoilerplate = function(sessId, sessVer) {
        var sessionId;
        var version = sessVer !== undefined ? sessVer : 2;
        if (sessId) {
            sessionId = sessId;
        } else {
            sessionId = SDPUtils.generateSessionId();
        }
        // FIXME: sess-id should be an NTP timestamp.
        return 'v=0\r\n' +
            'o=thisisadapterortc ' + sessionId + ' ' + version + ' IN IP4 127.0.0.1\r\n' +
            's=-\r\n' +
            't=0 0\r\n';
    };

    SDPUtils.writeMediaSection = function(transceiver, caps, type, stream) {
        var sdp = SDPUtils.writeRtpDescription(transceiver.kind, caps);

        // Map ICE parameters (ufrag, pwd) to SDP.
        sdp += SDPUtils.writeIceParameters(
            transceiver.iceGatherer.getLocalParameters());

        // Map DTLS parameters to SDP.
        sdp += SDPUtils.writeDtlsParameters(
            transceiver.dtlsTransport.getLocalParameters(),
            type === 'offer' ? 'actpass' : 'active');

        sdp += 'a=mid:' + transceiver.mid + '\r\n';

        if (transceiver.direction) {
            sdp += 'a=' + transceiver.direction + '\r\n';
        } else if (transceiver.rtpSender && transceiver.rtpReceiver) {
            sdp += 'a=sendrecv\r\n';
        } else if (transceiver.rtpSender) {
            sdp += 'a=sendonly\r\n';
        } else if (transceiver.rtpReceiver) {
            sdp += 'a=recvonly\r\n';
        } else {
            sdp += 'a=inactive\r\n';
        }

        if (transceiver.rtpSender) {
            // spec.
            var msid = 'msid:' + stream.id + ' ' +
                transceiver.rtpSender.track.id + '\r\n';
            sdp += 'a=' + msid;

            // for Chrome.
            sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].ssrc +
                ' ' + msid;
            if (transceiver.sendEncodingParameters[0].rtx) {
                sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].rtx.ssrc +
                    ' ' + msid;
                sdp += 'a=ssrc-group:FID ' +
                    transceiver.sendEncodingParameters[0].ssrc + ' ' +
                    transceiver.sendEncodingParameters[0].rtx.ssrc +
                    '\r\n';
            }
        }
        // FIXME: this should be written by writeRtpDescription.
        sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].ssrc +
            ' cname:' + SDPUtils.localCName + '\r\n';
        if (transceiver.rtpSender && transceiver.sendEncodingParameters[0].rtx) {
            sdp += 'a=ssrc:' + transceiver.sendEncodingParameters[0].rtx.ssrc +
                ' cname:' + SDPUtils.localCName + '\r\n';
        }
        return sdp;
    };

// Gets the direction from the mediaSection or the sessionpart.
    SDPUtils.getDirection = function(mediaSection, sessionpart) {
        // Look for sendrecv, sendonly, recvonly, inactive, default to sendrecv.
        var lines = SDPUtils.splitLines(mediaSection);
        for (var i = 0; i < lines.length; i++) {
            switch (lines[i]) {
                case 'a=sendrecv':
                case 'a=sendonly':
                case 'a=recvonly':
                case 'a=inactive':
                    return lines[i].substr(2);
                default:
                // FIXME: What should happen here?
            }
        }
        if (sessionpart) {
            return SDPUtils.getDirection(sessionpart);
        }
        return 'sendrecv';
    };

    SDPUtils.getKind = function(mediaSection) {
        var lines = SDPUtils.splitLines(mediaSection);
        var mline = lines[0].split(' ');
        return mline[0].substr(2);
    };

    SDPUtils.isRejected = function(mediaSection) {
        return mediaSection.split(' ', 2)[1] === '0';
    };

    SDPUtils.parseMLine = function(mediaSection) {
        var lines = SDPUtils.splitLines(mediaSection);
        var parts = lines[0].substr(2).split(' ');
        return {
            kind: parts[0],
            port: parseInt(parts[1], 10),
            protocol: parts[2],
            fmt: parts.slice(3).join(' ')
        };
    };

    SDPUtils.parseOLine = function(mediaSection) {
        var line = SDPUtils.matchPrefix(mediaSection, 'o=')[0];
        var parts = line.substr(2).split(' ');
        return {
            username: parts[0],
            sessionId: parts[1],
            sessionVersion: parseInt(parts[2], 10),
            netType: parts[3],
            addressType: parts[4],
            address: parts[5],
        };
    }

// Expose public methods.
    if (typeof module === 'object') {
        module.exports = SDPUtils;
    }

},{}],3:[function(require,module,exports){
    (function (global){
      /*
       *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
       *
       *  Use of this source code is governed by a BSD-style license
       *  that can be found in the LICENSE file in the root of the source
       *  tree.
       */
      /* eslint-env node */

        'use strict';

        var adapterFactory = require('./adapter_factory.js');
        module.exports = adapterFactory({window: global.window});

    }).call(this,typeof global !== "undefined" ? global : typeof self !== "undefined" ? self : typeof window !== "undefined" ? window : {})
},{"./adapter_factory.js":4}],4:[function(require,module,exports){
  /*
   *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
   *
   *  Use of this source code is governed by a BSD-style license
   *  that can be found in the LICENSE file in the root of the source
   *  tree.
   */
  /* eslint-env node */

    'use strict';

    var utils = require('./utils');
// Shimming starts here.
    module.exports = function(dependencies, opts) {
        var window = dependencies && dependencies.window;

        var options = {
            shimChrome: true,
            shimFirefox: true,
            shimEdge: true,
            shimSafari: true,
        };

        for (var key in opts) {
            if (hasOwnProperty.call(opts, key)) {
                options[key] = opts[key];
            }
        }

        // Utils.
        var logging = utils.log;
        var browserDetails = utils.detectBrowser(window);

        // Uncomment the line below if you want logging to occur, including logging
        // for the switch statement below. Can also be turned on in the browser via
        // adapter.disableLog(false), but then logging from the switch statement below
        // will not appear.
        // require('./utils').disableLog(false);

        // Browser shims.
        var chromeShim = require('./chrome/chrome_shim') || null;
        var edgeShim = require('./edge/edge_shim') || null;
        var firefoxShim = require('./firefox/firefox_shim') || null;
        var safariShim = require('./safari/safari_shim') || null;
        var commonShim = require('./common_shim') || null;

        // Export to the adapter global object visible in the browser.
        var adapter = {
            browserDetails: browserDetails,
            commonShim: commonShim,
            extractVersion: utils.extractVersion,
            disableLog: utils.disableLog,
            disableWarnings: utils.disableWarnings
        };

        // Shim browser if found.
        switch (browserDetails.browser) {
            case 'chrome':
                if (!chromeShim || !chromeShim.shimPeerConnection ||
                    !options.shimChrome) {
                    logging('Chrome shim is not included in this adapter release.');
                    return adapter;
                }
                logging('adapter.js shimming chrome.');
                // Export to the adapter global object visible in the browser.
                adapter.browserShim = chromeShim;
                commonShim.shimCreateObjectURL(window);

                chromeShim.shimGetUserMedia(window);
                chromeShim.shimMediaStream(window);
                chromeShim.shimSourceObject(window);
                chromeShim.shimPeerConnection(window);
                chromeShim.shimOnTrack(window);
                chromeShim.shimAddTrackRemoveTrack(window);
                chromeShim.shimGetSendersWithDtmf(window);
                chromeShim.shimSenderReceiverGetStats(window);

                commonShim.shimRTCIceCandidate(window);
                commonShim.shimMaxMessageSize(window);
                commonShim.shimSendThrowTypeError(window);
                break;
            case 'firefox':
                if (!firefoxShim || !firefoxShim.shimPeerConnection ||
                    !options.shimFirefox) {
                    logging('Firefox shim is not included in this adapter release.');
                    return adapter;
                }
                logging('adapter.js shimming firefox.');
                // Export to the adapter global object visible in the browser.
                adapter.browserShim = firefoxShim;
                commonShim.shimCreateObjectURL(window);

                firefoxShim.shimGetUserMedia(window);
                firefoxShim.shimSourceObject(window);
                firefoxShim.shimPeerConnection(window);
                firefoxShim.shimOnTrack(window);
                firefoxShim.shimRemoveStream(window);
                firefoxShim.shimSenderGetStats(window);
                firefoxShim.shimReceiverGetStats(window);
                firefoxShim.shimRTCDataChannel(window);

                commonShim.shimRTCIceCandidate(window);
                commonShim.shimMaxMessageSize(window);
                commonShim.shimSendThrowTypeError(window);
                break;
            case 'edge':
                if (!edgeShim || !edgeShim.shimPeerConnection || !options.shimEdge) {
                    logging('MS edge shim is not included in this adapter release.');
                    return adapter;
                }
                logging('adapter.js shimming edge.');
                // Export to the adapter global object visible in the browser.
                adapter.browserShim = edgeShim;
                commonShim.shimCreateObjectURL(window);

                edgeShim.shimGetUserMedia(window);
                edgeShim.shimPeerConnection(window);
                edgeShim.shimReplaceTrack(window);

                // the edge shim implements the full RTCIceCandidate object.

                commonShim.shimMaxMessageSize(window);
                commonShim.shimSendThrowTypeError(window);
                break;
            case 'safari':
                if (!safariShim || !options.shimSafari) {
                    logging('Safari shim is not included in this adapter release.');
                    return adapter;
                }
                logging('adapter.js shimming safari.');
                // Export to the adapter global object visible in the browser.
                adapter.browserShim = safariShim;
                commonShim.shimCreateObjectURL(window);

                safariShim.shimRTCIceServerUrls(window);
                safariShim.shimCallbacksAPI(window);
                safariShim.shimLocalStreamsAPI(window);
                safariShim.shimRemoteStreamsAPI(window);
                safariShim.shimTrackEventTransceiver(window);
                safariShim.shimGetUserMedia(window);
                safariShim.shimCreateOfferLegacy(window);

                commonShim.shimRTCIceCandidate(window);
                commonShim.shimMaxMessageSize(window);
                commonShim.shimSendThrowTypeError(window);
                break;
            default:
                logging('Unsupported browser!');
                break;
        }

        return adapter;
    };

},{"./chrome/chrome_shim":5,"./common_shim":7,"./edge/edge_shim":8,"./firefox/firefox_shim":11,"./safari/safari_shim":13,"./utils":14}],5:[function(require,module,exports){

  /*
   *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
   *
   *  Use of this source code is governed by a BSD-style license
   *  that can be found in the LICENSE file in the root of the source
   *  tree.
   */
  /* eslint-env node */
    'use strict';
    var utils = require('../utils.js');
    var logging = utils.log;

  /* iterates the stats graph recursively. */
    function walkStats(stats, base, resultSet) {
        if (!base || resultSet.has(base.id)) {
            return;
        }
        resultSet.set(base.id, base);
        Object.keys(base).forEach(function(name) {
            if (name.endsWith('Id')) {
                walkStats(stats, stats.get(base[name]), resultSet);
            } else if (name.endsWith('Ids')) {
                base[name].forEach(function(id) {
                    walkStats(stats, stats.get(id), resultSet);
                });
            }
        });
    }

  /* filter getStats for a sender/receiver track. */
    function filterStats(result, track, outbound) {
        var streamStatsType = outbound ? 'outbound-rtp' : 'inbound-rtp';
        var filteredResult = new Map();
        if (track === null) {
            return filteredResult;
        }
        var trackStats = [];
        result.forEach(function(value) {
            if (value.type === 'track' &&
                value.trackIdentifier === track.id) {
                trackStats.push(value);
            }
        });
        trackStats.forEach(function(trackStat) {
            result.forEach(function(stats) {
                if (stats.type === streamStatsType && stats.trackId === trackStat.id) {
                    walkStats(result, stats, filteredResult);
                }
            });
        });
        return filteredResult;
    }

    module.exports = {
        shimGetUserMedia: require('./getusermedia'),
        shimMediaStream: function(window) {
            window.MediaStream = window.MediaStream || window.webkitMediaStream;
        },

        shimOnTrack: function(window) {
            if (typeof window === 'object' && window.RTCPeerConnection && !('ontrack' in
                window.RTCPeerConnection.prototype)) {
                Object.defineProperty(window.RTCPeerConnection.prototype, 'ontrack', {
                    get: function() {
                        return this._ontrack;
                    },
                    set: function(f) {
                        if (this._ontrack) {
                            this.removeEventListener('track', this._ontrack);
                        }
                        this.addEventListener('track', this._ontrack = f);
                    }
                });
                var origSetRemoteDescription =
                    window.RTCPeerConnection.prototype.setRemoteDescription;
                window.RTCPeerConnection.prototype.setRemoteDescription = function() {
                    var pc = this;
                    if (!pc._ontrackpoly) {
                        pc._ontrackpoly = function(e) {
                            // onaddstream does not fire when a track is added to an existing
                            // stream. But stream.onaddtrack is implemented so we use that.
                            e.stream.addEventListener('addtrack', function(te) {
                                var receiver;
                                if (window.RTCPeerConnection.prototype.getReceivers) {
                                    receiver = pc.getReceivers().find(function(r) {
                                        return r.track && r.track.id === te.track.id;
                                    });
                                } else {
                                    receiver = {track: te.track};
                                }

                                var event = new Event('track');
                                event.track = te.track;
                                event.receiver = receiver;
                                event.transceiver = {receiver: receiver};
                                event.streams = [e.stream];
                                pc.dispatchEvent(event);
                            });
                            e.stream.getTracks().forEach(function(track) {
                                var receiver;
                                if (window.RTCPeerConnection.prototype.getReceivers) {
                                    receiver = pc.getReceivers().find(function(r) {
                                        return r.track && r.track.id === track.id;
                                    });
                                } else {
                                    receiver = {track: track};
                                }
                                var event = new Event('track');
                                event.track = track;
                                event.receiver = receiver;
                                event.transceiver = {receiver: receiver};
                                event.streams = [e.stream];
                                pc.dispatchEvent(event);
                            });
                        };
                        pc.addEventListener('addstream', pc._ontrackpoly);
                    }
                    return origSetRemoteDescription.apply(pc, arguments);
                };
            } else if (!('RTCRtpTransceiver' in window)) {
                utils.wrapPeerConnectionEvent(window, 'track', function(e) {
                    if (!e.transceiver) {
                        e.transceiver = {receiver: e.receiver};
                    }
                    return e;
                });
            }
        },

        shimGetSendersWithDtmf: function(window) {
            // Overrides addTrack/removeTrack, depends on shimAddTrackRemoveTrack.
            if (typeof window === 'object' && window.RTCPeerConnection &&
                !('getSenders' in window.RTCPeerConnection.prototype) &&
                'createDTMFSender' in window.RTCPeerConnection.prototype) {
                var shimSenderWithDtmf = function(pc, track) {
                    return {
                        track: track,
                        get dtmf() {
                            if (this._dtmf === undefined) {
                                if (track.kind === 'audio') {
                                    this._dtmf = pc.createDTMFSender(track);
                                } else {
                                    this._dtmf = null;
                                }
                            }
                            return this._dtmf;
                        },
                        _pc: pc
                    };
                };

                // augment addTrack when getSenders is not available.
                if (!window.RTCPeerConnection.prototype.getSenders) {
                    window.RTCPeerConnection.prototype.getSenders = function() {
                        this._senders = this._senders || [];
                        return this._senders.slice(); // return a copy of the internal state.
                    };
                    var origAddTrack = window.RTCPeerConnection.prototype.addTrack;
                    window.RTCPeerConnection.prototype.addTrack = function(track, stream) {
                        var pc = this;
                        var sender = origAddTrack.apply(pc, arguments);
                        if (!sender) {
                            sender = shimSenderWithDtmf(pc, track);
                            pc._senders.push(sender);
                        }
                        return sender;
                    };

                    var origRemoveTrack = window.RTCPeerConnection.prototype.removeTrack;
                    window.RTCPeerConnection.prototype.removeTrack = function(sender) {
                        var pc = this;
                        origRemoveTrack.apply(pc, arguments);
                        var idx = pc._senders.indexOf(sender);
                        if (idx !== -1) {
                            pc._senders.splice(idx, 1);
                        }
                    };
                }
                var origAddStream = window.RTCPeerConnection.prototype.addStream;
                window.RTCPeerConnection.prototype.addStream = function(stream) {
                    var pc = this;
                    pc._senders = pc._senders || [];
                    origAddStream.apply(pc, [stream]);
                    stream.getTracks().forEach(function(track) {
                        pc._senders.push(shimSenderWithDtmf(pc, track));
                    });
                };

                var origRemoveStream = window.RTCPeerConnection.prototype.removeStream;
                window.RTCPeerConnection.prototype.removeStream = function(stream) {
                    var pc = this;
                    pc._senders = pc._senders || [];
                    origRemoveStream.apply(pc, [stream]);

                    stream.getTracks().forEach(function(track) {
                        var sender = pc._senders.find(function(s) {
                            return s.track === track;
                        });
                        if (sender) {
                            pc._senders.splice(pc._senders.indexOf(sender), 1); // remove sender
                        }
                    });
                };
            } else if (typeof window === 'object' && window.RTCPeerConnection &&
                'getSenders' in window.RTCPeerConnection.prototype &&
                'createDTMFSender' in window.RTCPeerConnection.prototype &&
                window.RTCRtpSender &&
                !('dtmf' in window.RTCRtpSender.prototype)) {
                var origGetSenders = window.RTCPeerConnection.prototype.getSenders;
                window.RTCPeerConnection.prototype.getSenders = function() {
                    var pc = this;
                    var senders = origGetSenders.apply(pc, []);
                    senders.forEach(function(sender) {
                        sender._pc = pc;
                    });
                    return senders;
                };

                Object.defineProperty(window.RTCRtpSender.prototype, 'dtmf', {
                    get: function() {
                        if (this._dtmf === undefined) {
                            if (this.track.kind === 'audio') {
                                this._dtmf = this._pc.createDTMFSender(this.track);
                            } else {
                                this._dtmf = null;
                            }
                        }
                        return this._dtmf;
                    }
                });
            }
        },

        shimSenderReceiverGetStats: function(window) {
            if (!(typeof window === 'object' && window.RTCPeerConnection &&
                window.RTCRtpSender && window.RTCRtpReceiver)) {
                return;
            }

            // shim sender stats.
            if (!('getStats' in window.RTCRtpSender.prototype)) {
                var origGetSenders = window.RTCPeerConnection.prototype.getSenders;
                if (origGetSenders) {
                    window.RTCPeerConnection.prototype.getSenders = function() {
                        var pc = this;
                        var senders = origGetSenders.apply(pc, []);
                        senders.forEach(function(sender) {
                            sender._pc = pc;
                        });
                        return senders;
                    };
                }

                var origAddTrack = window.RTCPeerConnection.prototype.addTrack;
                if (origAddTrack) {
                    window.RTCPeerConnection.prototype.addTrack = function() {
                        var sender = origAddTrack.apply(this, arguments);
                        sender._pc = this;
                        return sender;
                    };
                }
                window.RTCRtpSender.prototype.getStats = function() {
                    var sender = this;
                    return this._pc.getStats().then(function(result) {
                      /* Note: this will include stats of all senders that
                       *   send a track with the same id as sender.track as
                       *   it is not possible to identify the RTCRtpSender.
                       */
                        return filterStats(result, sender.track, true);
                    });
                };
            }

            // shim receiver stats.
            if (!('getStats' in window.RTCRtpReceiver.prototype)) {
                var origGetReceivers = window.RTCPeerConnection.prototype.getReceivers;
                if (origGetReceivers) {
                    window.RTCPeerConnection.prototype.getReceivers = function() {
                        var pc = this;
                        var receivers = origGetReceivers.apply(pc, []);
                        receivers.forEach(function(receiver) {
                            receiver._pc = pc;
                        });
                        return receivers;
                    };
                }
                utils.wrapPeerConnectionEvent(window, 'track', function(e) {
                    e.receiver._pc = e.srcElement;
                    return e;
                });
                window.RTCRtpReceiver.prototype.getStats = function() {
                    var receiver = this;
                    return this._pc.getStats().then(function(result) {
                        return filterStats(result, receiver.track, false);
                    });
                };
            }

            if (!('getStats' in window.RTCRtpSender.prototype &&
                'getStats' in window.RTCRtpReceiver.prototype)) {
                return;
            }

            // shim RTCPeerConnection.getStats(track).
            var origGetStats = window.RTCPeerConnection.prototype.getStats;
            window.RTCPeerConnection.prototype.getStats = function() {
                var pc = this;
                if (arguments.length > 0 &&
                    arguments[0] instanceof window.MediaStreamTrack) {
                    var track = arguments[0];
                    var sender;
                    var receiver;
                    var err;
                    pc.getSenders().forEach(function(s) {
                        if (s.track === track) {
                            if (sender) {
                                err = true;
                            } else {
                                sender = s;
                            }
                        }
                    });
                    pc.getReceivers().forEach(function(r) {
                        if (r.track === track) {
                            if (receiver) {
                                err = true;
                            } else {
                                receiver = r;
                            }
                        }
                        return r.track === track;
                    });
                    if (err || (sender && receiver)) {
                        return Promise.reject(new DOMException(
                            'There are more than one sender or receiver for the track.',
                            'InvalidAccessError'));
                    } else if (sender) {
                        return sender.getStats();
                    } else if (receiver) {
                        return receiver.getStats();
                    }
                    return Promise.reject(new DOMException(
                        'There is no sender or receiver for the track.',
                        'InvalidAccessError'));
                }
                return origGetStats.apply(pc, arguments);
            };
        },

        shimSourceObject: function(window) {
            var URL = window && window.URL;

            if (typeof window === 'object') {
                if (window.HTMLMediaElement &&
                    !('srcObject' in window.HTMLMediaElement.prototype)) {
                    // Shim the srcObject property, once, when HTMLMediaElement is found.
                    Object.defineProperty(window.HTMLMediaElement.prototype, 'srcObject', {
                        get: function() {
                            return this._srcObject;
                        },
                        set: function(stream) {
                            var self = this;
                            // Use _srcObject as a private property for this shim
                            this._srcObject = stream;
                            if (this.src) {
                                URL.revokeObjectURL(this.src);
                            }

                            if (!stream) {
                                this.src = '';
                                return undefined;
                            }
                            this.src = URL.createObjectURL(stream);
                            // We need to recreate the blob url when a track is added or
                            // removed. Doing it manually since we want to avoid a recursion.
                            stream.addEventListener('addtrack', function() {
                                if (self.src) {
                                    URL.revokeObjectURL(self.src);
                                }
                                self.src = URL.createObjectURL(stream);
                            });
                            stream.addEventListener('removetrack', function() {
                                if (self.src) {
                                    URL.revokeObjectURL(self.src);
                                }
                                self.src = URL.createObjectURL(stream);
                            });
                        }
                    });
                }
            }
        },

        shimAddTrackRemoveTrackWithNative: function(window) {
            // shim addTrack/removeTrack with native variants in order to make
            // the interactions with legacy getLocalStreams behave as in other browsers.
            // Keeps a mapping stream.id => [stream, rtpsenders...]
            window.RTCPeerConnection.prototype.getLocalStreams = function() {
                var pc = this;
                this._shimmedLocalStreams = this._shimmedLocalStreams || {};
                return Object.keys(this._shimmedLocalStreams).map(function(streamId) {
                    return pc._shimmedLocalStreams[streamId][0];
                });
            };

            var origAddTrack = window.RTCPeerConnection.prototype.addTrack;
            window.RTCPeerConnection.prototype.addTrack = function(track, stream) {
                if (!stream) {
                    return origAddTrack.apply(this, arguments);
                }
                this._shimmedLocalStreams = this._shimmedLocalStreams || {};

                var sender = origAddTrack.apply(this, arguments);
                if (!this._shimmedLocalStreams[stream.id]) {
                    this._shimmedLocalStreams[stream.id] = [stream, sender];
                } else if (this._shimmedLocalStreams[stream.id].indexOf(sender) === -1) {
                    this._shimmedLocalStreams[stream.id].push(sender);
                }
                return sender;
            };

            var origAddStream = window.RTCPeerConnection.prototype.addStream;
            window.RTCPeerConnection.prototype.addStream = function(stream) {
                var pc = this;
                this._shimmedLocalStreams = this._shimmedLocalStreams || {};

                stream.getTracks().forEach(function(track) {
                    var alreadyExists = pc.getSenders().find(function(s) {
                        return s.track === track;
                    });
                    if (alreadyExists) {
                        throw new DOMException('Track already exists.',
                            'InvalidAccessError');
                    }
                });
                var existingSenders = pc.getSenders();
                origAddStream.apply(this, arguments);
                var newSenders = pc.getSenders().filter(function(newSender) {
                    return existingSenders.indexOf(newSender) === -1;
                });
                this._shimmedLocalStreams[stream.id] = [stream].concat(newSenders);
            };

            var origRemoveStream = window.RTCPeerConnection.prototype.removeStream;
            window.RTCPeerConnection.prototype.removeStream = function(stream) {
                this._shimmedLocalStreams = this._shimmedLocalStreams || {};
                delete this._shimmedLocalStreams[stream.id];
                return origRemoveStream.apply(this, arguments);
            };

            var origRemoveTrack = window.RTCPeerConnection.prototype.removeTrack;
            window.RTCPeerConnection.prototype.removeTrack = function(sender) {
                var pc = this;
                this._shimmedLocalStreams = this._shimmedLocalStreams || {};
                if (sender) {
                    Object.keys(this._shimmedLocalStreams).forEach(function(streamId) {
                        var idx = pc._shimmedLocalStreams[streamId].indexOf(sender);
                        if (idx !== -1) {
                            pc._shimmedLocalStreams[streamId].splice(idx, 1);
                        }
                        if (pc._shimmedLocalStreams[streamId].length === 1) {
                            delete pc._shimmedLocalStreams[streamId];
                        }
                    });
                }
                return origRemoveTrack.apply(this, arguments);
            };
        },

        shimAddTrackRemoveTrack: function(window) {
            var browserDetails = utils.detectBrowser(window);
            // shim addTrack and removeTrack.
            if (window.RTCPeerConnection.prototype.addTrack &&
                browserDetails.version >= 65) {
                return this.shimAddTrackRemoveTrackWithNative(window);
            }

            // also shim pc.getLocalStreams when addTrack is shimmed
            // to return the original streams.
            var origGetLocalStreams = window.RTCPeerConnection.prototype
                .getLocalStreams;
            window.RTCPeerConnection.prototype.getLocalStreams = function() {
                var pc = this;
                var nativeStreams = origGetLocalStreams.apply(this);
                pc._reverseStreams = pc._reverseStreams || {};
                return nativeStreams.map(function(stream) {
                    return pc._reverseStreams[stream.id];
                });
            };

            var origAddStream = window.RTCPeerConnection.prototype.addStream;
            window.RTCPeerConnection.prototype.addStream = function(stream) {
                var pc = this;
                pc._streams = pc._streams || {};
                pc._reverseStreams = pc._reverseStreams || {};

                stream.getTracks().forEach(function(track) {
                    var alreadyExists = pc.getSenders().find(function(s) {
                        return s.track === track;
                    });
                    if (alreadyExists) {
                        throw new DOMException('Track already exists.',
                            'InvalidAccessError');
                    }
                });
                // Add identity mapping for consistency with addTrack.
                // Unless this is being used with a stream from addTrack.
                if (!pc._reverseStreams[stream.id]) {
                    var newStream = new window.MediaStream(stream.getTracks());
                    pc._streams[stream.id] = newStream;
                    pc._reverseStreams[newStream.id] = stream;
                    stream = newStream;
                }
                origAddStream.apply(pc, [stream]);
            };

            var origRemoveStream = window.RTCPeerConnection.prototype.removeStream;
            window.RTCPeerConnection.prototype.removeStream = function(stream) {
                var pc = this;
                pc._streams = pc._streams || {};
                pc._reverseStreams = pc._reverseStreams || {};

                origRemoveStream.apply(pc, [(pc._streams[stream.id] || stream)]);
                delete pc._reverseStreams[(pc._streams[stream.id] ?
                    pc._streams[stream.id].id : stream.id)];
                delete pc._streams[stream.id];
            };

            window.RTCPeerConnection.prototype.addTrack = function(track, stream) {
                var pc = this;
                if (pc.signalingState === 'closed') {
                    throw new DOMException(
                        'The RTCPeerConnection\'s signalingState is \'closed\'.',
                        'InvalidStateError');
                }
                var streams = [].slice.call(arguments, 1);
                if (streams.length !== 1 ||
                    !streams[0].getTracks().find(function(t) {
                        return t === track;
                    })) {
                    // this is not fully correct but all we can manage without
                    // [[associated MediaStreams]] internal slot.
                    throw new DOMException(
                        'The adapter.js addTrack polyfill only supports a single ' +
                        ' stream which is associated with the specified track.',
                        'NotSupportedError');
                }

                var alreadyExists = pc.getSenders().find(function(s) {
                    return s.track === track;
                });
                if (alreadyExists) {
                    throw new DOMException('Track already exists.',
                        'InvalidAccessError');
                }

                pc._streams = pc._streams || {};
                pc._reverseStreams = pc._reverseStreams || {};
                var oldStream = pc._streams[stream.id];
                if (oldStream) {
                    // this is using odd Chrome behaviour, use with caution:
                    // https://bugs.chromium.org/p/webrtc/issues/detail?id=7815
                    // Note: we rely on the high-level addTrack/dtmf shim to
                    // create the sender with a dtmf sender.
                    oldStream.addTrack(track);

                    // Trigger ONN async.
                    Promise.resolve().then(function() {
                        pc.dispatchEvent(new Event('negotiationneeded'));
                    });
                } else {
                    var newStream = new window.MediaStream([track]);
                    pc._streams[stream.id] = newStream;
                    pc._reverseStreams[newStream.id] = stream;
                    pc.addStream(newStream);
                }
                return pc.getSenders().find(function(s) {
                    return s.track === track;
                });
            };

            // replace the internal stream id with the external one and
            // vice versa.
            function replaceInternalStreamId(pc, description) {
                var sdp = description.sdp;
                Object.keys(pc._reverseStreams || []).forEach(function(internalId) {
                    var externalStream = pc._reverseStreams[internalId];
                    var internalStream = pc._streams[externalStream.id];
                    sdp = sdp.replace(new RegExp(internalStream.id, 'g'),
                        externalStream.id);
                });
                return new RTCSessionDescription({
                    type: description.type,
                    sdp: sdp
                });
            }
            function replaceExternalStreamId(pc, description) {
                var sdp = description.sdp;
                Object.keys(pc._reverseStreams || []).forEach(function(internalId) {
                    var externalStream = pc._reverseStreams[internalId];
                    var internalStream = pc._streams[externalStream.id];
                    sdp = sdp.replace(new RegExp(externalStream.id, 'g'),
                        internalStream.id);
                });
                return new RTCSessionDescription({
                    type: description.type,
                    sdp: sdp
                });
            }
            ['createOffer', 'createAnswer'].forEach(function(method) {
                var nativeMethod = window.RTCPeerConnection.prototype[method];
                window.RTCPeerConnection.prototype[method] = function() {
                    var pc = this;
                    var args = arguments;
                    var isLegacyCall = arguments.length &&
                        typeof arguments[0] === 'function';
                    if (isLegacyCall) {
                        return nativeMethod.apply(pc, [
                            function(description) {
                                var desc = replaceInternalStreamId(pc, description);
                                args[0].apply(null, [desc]);
                            },
                            function(err) {
                                if (args[1]) {
                                    args[1].apply(null, err);
                                }
                            }, arguments[2]
                        ]);
                    }
                    return nativeMethod.apply(pc, arguments)
                        .then(function(description) {
                            return replaceInternalStreamId(pc, description);
                        });
                };
            });

            var origSetLocalDescription =
                window.RTCPeerConnection.prototype.setLocalDescription;
            window.RTCPeerConnection.prototype.setLocalDescription = function() {
                var pc = this;
                if (!arguments.length || !arguments[0].type) {
                    return origSetLocalDescription.apply(pc, arguments);
                }
                arguments[0] = replaceExternalStreamId(pc, arguments[0]);
                return origSetLocalDescription.apply(pc, arguments);
            };

            // TODO: mangle getStats: https://w3c.github.io/webrtc-stats/#dom-rtcmediastreamstats-streamidentifier

            var origLocalDescription = Object.getOwnPropertyDescriptor(
                window.RTCPeerConnection.prototype, 'localDescription');
            Object.defineProperty(window.RTCPeerConnection.prototype,
                'localDescription', {
                    get: function() {
                        var pc = this;
                        var description = origLocalDescription.get.apply(this);
                        if (description.type === '') {
                            return description;
                        }
                        return replaceInternalStreamId(pc, description);
                    }
                });

            window.RTCPeerConnection.prototype.removeTrack = function(sender) {
                var pc = this;
                if (pc.signalingState === 'closed') {
                    throw new DOMException(
                        'The RTCPeerConnection\'s signalingState is \'closed\'.',
                        'InvalidStateError');
                }
                // We can not yet check for sender instanceof RTCRtpSender
                // since we shim RTPSender. So we check if sender._pc is set.
                if (!sender._pc) {
                    throw new DOMException('Argument 1 of RTCPeerConnection.removeTrack ' +
                        'does not implement interface RTCRtpSender.', 'TypeError');
                }
                var isLocal = sender._pc === pc;
                if (!isLocal) {
                    throw new DOMException('Sender was not created by this connection.',
                        'InvalidAccessError');
                }

                // Search for the native stream the senders track belongs to.
                pc._streams = pc._streams || {};
                var stream;
                Object.keys(pc._streams).forEach(function(streamid) {
                    var hasTrack = pc._streams[streamid].getTracks().find(function(track) {
                        return sender.track === track;
                    });
                    if (hasTrack) {
                        stream = pc._streams[streamid];
                    }
                });

                if (stream) {
                    if (stream.getTracks().length === 1) {
                        // if this is the last track of the stream, remove the stream. This
                        // takes care of any shimmed _senders.
                        pc.removeStream(pc._reverseStreams[stream.id]);
                    } else {
                        // relying on the same odd chrome behaviour as above.
                        stream.removeTrack(sender.track);
                    }
                    pc.dispatchEvent(new Event('negotiationneeded'));
                }
            };
        },

        shimPeerConnection: function(window) {
            var browserDetails = utils.detectBrowser(window);

            // The RTCPeerConnection object.
            if (!window.RTCPeerConnection && window.webkitRTCPeerConnection) {
                window.RTCPeerConnection = function(pcConfig, pcConstraints) {
                    // Translate iceTransportPolicy to iceTransports,
                    // see https://code.google.com/p/webrtc/issues/detail?id=4869
                    // this was fixed in M56 along with unprefixing RTCPeerConnection.
                    logging('PeerConnection');
                    if (pcConfig && pcConfig.iceTransportPolicy) {
                        pcConfig.iceTransports = pcConfig.iceTransportPolicy;
                    }

                    return new window.webkitRTCPeerConnection(pcConfig, pcConstraints);
                };
                window.RTCPeerConnection.prototype =
                    window.webkitRTCPeerConnection.prototype;
                // wrap static methods. Currently just generateCertificate.
                if (window.webkitRTCPeerConnection.generateCertificate) {
                    Object.defineProperty(window.RTCPeerConnection, 'generateCertificate', {
                        get: function() {
                            return window.webkitRTCPeerConnection.generateCertificate;
                        }
                    });
                }
            } else {
                // migrate from non-spec RTCIceServer.url to RTCIceServer.urls
                var OrigPeerConnection = window.RTCPeerConnection;
                window.RTCPeerConnection = function(pcConfig, pcConstraints) {
                    if (pcConfig && pcConfig.iceServers) {
                        var newIceServers = [];
                        for (var i = 0; i < pcConfig.iceServers.length; i++) {
                            var server = pcConfig.iceServers[i];
                            if (!server.hasOwnProperty('urls') &&
                                server.hasOwnProperty('url')) {
                                utils.deprecated('RTCIceServer.url', 'RTCIceServer.urls');
                                server = JSON.parse(JSON.stringify(server));
                                server.urls = server.url;
                                newIceServers.push(server);
                            } else {
                                newIceServers.push(pcConfig.iceServers[i]);
                            }
                        }
                        pcConfig.iceServers = newIceServers;
                    }
                    return new OrigPeerConnection(pcConfig, pcConstraints);
                };
                window.RTCPeerConnection.prototype = OrigPeerConnection.prototype;
                // wrap static methods. Currently just generateCertificate.
                Object.defineProperty(window.RTCPeerConnection, 'generateCertificate', {
                    get: function() {
                        return OrigPeerConnection.generateCertificate;
                    }
                });
            }

            var origGetStats = window.RTCPeerConnection.prototype.getStats;
            window.RTCPeerConnection.prototype.getStats = function(selector,
                                                                   successCallback, errorCallback) {
                var pc = this;
                var args = arguments;

                // If selector is a function then we are in the old style stats so just
                // pass back the original getStats format to avoid breaking old users.
                if (arguments.length > 0 && typeof selector === 'function') {
                    return origGetStats.apply(this, arguments);
                }

                // When spec-style getStats is supported, return those when called with
                // either no arguments or the selector argument is null.
                if (origGetStats.length === 0 && (arguments.length === 0 ||
                    typeof arguments[0] !== 'function')) {
                    return origGetStats.apply(this, []);
                }

                var fixChromeStats_ = function(response) {
                    var standardReport = {};
                    var reports = response.result();
                    reports.forEach(function(report) {
                        var standardStats = {
                            id: report.id,
                            timestamp: report.timestamp,
                            type: {
                                localcandidate: 'local-candidate',
                                remotecandidate: 'remote-candidate'
                            }[report.type] || report.type
                        };
                        report.names().forEach(function(name) {
                            standardStats[name] = report.stat(name);
                        });
                        standardReport[standardStats.id] = standardStats;
                    });

                    return standardReport;
                };

                // shim getStats with maplike support
                var makeMapStats = function(stats) {
                    return new Map(Object.keys(stats).map(function(key) {
                        return [key, stats[key]];
                    }));
                };

                if (arguments.length >= 2) {
                    var successCallbackWrapper_ = function(response) {
                        args[1](makeMapStats(fixChromeStats_(response)));
                    };

                    return origGetStats.apply(this, [successCallbackWrapper_,
                        arguments[0]]);
                }

                // promise-support
                return new Promise(function(resolve, reject) {
                    origGetStats.apply(pc, [
                        function(response) {
                            resolve(makeMapStats(fixChromeStats_(response)));
                        }, reject]);
                }).then(successCallback, errorCallback);
            };

            // add promise support -- natively available in Chrome 51
            if (browserDetails.version < 51) {
                ['setLocalDescription', 'setRemoteDescription', 'addIceCandidate']
                    .forEach(function(method) {
                        var nativeMethod = window.RTCPeerConnection.prototype[method];
                        window.RTCPeerConnection.prototype[method] = function() {
                            var args = arguments;
                            var pc = this;
                            var promise = new Promise(function(resolve, reject) {
                                nativeMethod.apply(pc, [args[0], resolve, reject]);
                            });
                            if (args.length < 2) {
                                return promise;
                            }
                            return promise.then(function() {
                                    args[1].apply(null, []);
                                },
                                function(err) {
                                    if (args.length >= 3) {
                                        args[2].apply(null, [err]);
                                    }
                                });
                        };
                    });
            }

            // promise support for createOffer and createAnswer. Available (without
            // bugs) since M52: crbug/619289
            if (browserDetails.version < 52) {
                ['createOffer', 'createAnswer'].forEach(function(method) {
                    var nativeMethod = window.RTCPeerConnection.prototype[method];
                    window.RTCPeerConnection.prototype[method] = function() {
                        var pc = this;
                        if (arguments.length < 1 || (arguments.length === 1 &&
                            typeof arguments[0] === 'object')) {
                            var opts = arguments.length === 1 ? arguments[0] : undefined;
                            return new Promise(function(resolve, reject) {
                                nativeMethod.apply(pc, [resolve, reject, opts]);
                            });
                        }
                        return nativeMethod.apply(this, arguments);
                    };
                });
            }

            // shim implicit creation of RTCSessionDescription/RTCIceCandidate
            ['setLocalDescription', 'setRemoteDescription', 'addIceCandidate']
                .forEach(function(method) {
                    var nativeMethod = window.RTCPeerConnection.prototype[method];
                    window.RTCPeerConnection.prototype[method] = function() {
                        arguments[0] = new ((method === 'addIceCandidate') ?
                            window.RTCIceCandidate :
                            window.RTCSessionDescription)(arguments[0]);
                        return nativeMethod.apply(this, arguments);
                    };
                });

            // support for addIceCandidate(null or undefined)
            var nativeAddIceCandidate =
                window.RTCPeerConnection.prototype.addIceCandidate;
            window.RTCPeerConnection.prototype.addIceCandidate = function() {
                if (!arguments[0]) {
                    if (arguments[1]) {
                        arguments[1].apply(null);
                    }
                    return Promise.resolve();
                }
                return nativeAddIceCandidate.apply(this, arguments);
            };
        }
    };

},{"../utils.js":14,"./getusermedia":6}],6:[function(require,module,exports){
  /*
   *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
   *
   *  Use of this source code is governed by a BSD-style license
   *  that can be found in the LICENSE file in the root of the source
   *  tree.
   */
  /* eslint-env node */
    'use strict';
    var utils = require('../utils.js');
    var logging = utils.log;

// Expose public methods.
    module.exports = function(window) {
        var browserDetails = utils.detectBrowser(window);
        var navigator = window && window.navigator;

        var constraintsToChrome_ = function(c) {
            if (typeof c !== 'object' || c.mandatory || c.optional) {
                return c;
            }
            var cc = {};
            Object.keys(c).forEach(function(key) {
                if (key === 'require' || key === 'advanced' || key === 'mediaSource') {
                    return;
                }
                var r = (typeof c[key] === 'object') ? c[key] : {ideal: c[key]};
                if (r.exact !== undefined && typeof r.exact === 'number') {
                    r.min = r.max = r.exact;
                }
                var oldname_ = function(prefix, name) {
                    if (prefix) {
                        return prefix + name.charAt(0).toUpperCase() + name.slice(1);
                    }
                    return (name === 'deviceId') ? 'sourceId' : name;
                };
                if (r.ideal !== undefined) {
                    cc.optional = cc.optional || [];
                    var oc = {};
                    if (typeof r.ideal === 'number') {
                        oc[oldname_('min', key)] = r.ideal;
                        cc.optional.push(oc);
                        oc = {};
                        oc[oldname_('max', key)] = r.ideal;
                        cc.optional.push(oc);
                    } else {
                        oc[oldname_('', key)] = r.ideal;
                        cc.optional.push(oc);
                    }
                }
                if (r.exact !== undefined && typeof r.exact !== 'number') {
                    cc.mandatory = cc.mandatory || {};
                    cc.mandatory[oldname_('', key)] = r.exact;
                } else {
                    ['min', 'max'].forEach(function(mix) {
                        if (r[mix] !== undefined) {
                            cc.mandatory = cc.mandatory || {};
                            cc.mandatory[oldname_(mix, key)] = r[mix];
                        }
                    });
                }
            });
            if (c.advanced) {
                cc.optional = (cc.optional || []).concat(c.advanced);
            }
            return cc;
        };

        var shimConstraints_ = function(constraints, func) {
            if (browserDetails.version >= 61) {
                return func(constraints);
            }
            constraints = JSON.parse(JSON.stringify(constraints));
            if (constraints && typeof constraints.audio === 'object') {
                var remap = function(obj, a, b) {
                    if (a in obj && !(b in obj)) {
                        obj[b] = obj[a];
                        delete obj[a];
                    }
                };
                constraints = JSON.parse(JSON.stringify(constraints));
                remap(constraints.audio, 'autoGainControl', 'googAutoGainControl');
                remap(constraints.audio, 'noiseSuppression', 'googNoiseSuppression');
                constraints.audio = constraintsToChrome_(constraints.audio);
            }
            if (constraints && typeof constraints.video === 'object') {
                // Shim facingMode for mobile & surface pro.
                var face = constraints.video.facingMode;
                face = face && ((typeof face === 'object') ? face : {ideal: face});
                var getSupportedFacingModeLies = browserDetails.version < 66;

                if ((face && (face.exact === 'user' || face.exact === 'environment' ||
                    face.ideal === 'user' || face.ideal === 'environment')) &&
                    !(navigator.mediaDevices.getSupportedConstraints &&
                    navigator.mediaDevices.getSupportedConstraints().facingMode &&
                    !getSupportedFacingModeLies)) {
                    delete constraints.video.facingMode;
                    var matches;
                    if (face.exact === 'environment' || face.ideal === 'environment') {
                        matches = ['back', 'rear'];
                    } else if (face.exact === 'user' || face.ideal === 'user') {
                        matches = ['front'];
                    }
                    if (matches) {
                        // Look for matches in label, or use last cam for back (typical).
                        return navigator.mediaDevices.enumerateDevices()
                            .then(function(devices) {
                                devices = devices.filter(function(d) {
                                    return d.kind === 'videoinput';
                                });
                                var dev = devices.find(function(d) {
                                    return matches.some(function(match) {
                                        return d.label.toLowerCase().indexOf(match) !== -1;
                                    });
                                });
                                if (!dev && devices.length && matches.indexOf('back') !== -1) {
                                    dev = devices[devices.length - 1]; // more likely the back cam
                                }
                                if (dev) {
                                    constraints.video.deviceId = face.exact ? {exact: dev.deviceId} :
                                        {ideal: dev.deviceId};
                                }
                                constraints.video = constraintsToChrome_(constraints.video);
                                logging('chrome: ' + JSON.stringify(constraints));
                                return func(constraints);
                            });
                    }
                }
                constraints.video = constraintsToChrome_(constraints.video);
            }
            logging('chrome: ' + JSON.stringify(constraints));
            return func(constraints);
        };

        var shimError_ = function(e) {
            return {
                name: {
                    PermissionDeniedError: 'NotAllowedError',
                    PermissionDismissedError: 'NotAllowedError',
                    InvalidStateError: 'NotAllowedError',
                    DevicesNotFoundError: 'NotFoundError',
                    ConstraintNotSatisfiedError: 'OverconstrainedError',
                    TrackStartError: 'NotReadableError',
                    MediaDeviceFailedDueToShutdown: 'NotAllowedError',
                    MediaDeviceKillSwitchOn: 'NotAllowedError',
                    TabCaptureError: 'AbortError',
                    ScreenCaptureError: 'AbortError',
                    DeviceCaptureError: 'AbortError'
                }[e.name] || e.name,
                message: e.message,
                constraint: e.constraintName,
                toString: function() {
                    return this.name + (this.message && ': ') + this.message;
                }
            };
        };

        var getUserMedia_ = function(constraints, onSuccess, onError) {
            shimConstraints_(constraints, function(c) {
                navigator.webkitGetUserMedia(c, onSuccess, function(e) {
                    if (onError) {
                        onError(shimError_(e));
                    }
                });
            });
        };

        navigator.getUserMedia = getUserMedia_;

        // Returns the result of getUserMedia as a Promise.
        var getUserMediaPromise_ = function(constraints) {
            return new Promise(function(resolve, reject) {
                navigator.getUserMedia(constraints, resolve, reject);
            });
        };

        if (!navigator.mediaDevices) {
            navigator.mediaDevices = {
                getUserMedia: getUserMediaPromise_,
                enumerateDevices: function() {
                    return new Promise(function(resolve) {
                        var kinds = {audio: 'audioinput', video: 'videoinput'};
                        return window.MediaStreamTrack.getSources(function(devices) {
                            resolve(devices.map(function(device) {
                                return {label: device.label,
                                    kind: kinds[device.kind],
                                    deviceId: device.id,
                                    groupId: ''};
                            }));
                        });
                    });
                },
                getSupportedConstraints: function() {
                    return {
                        deviceId: true, echoCancellation: true, facingMode: true,
                        frameRate: true, height: true, width: true
                    };
                }
            };
        }

        // A shim for getUserMedia method on the mediaDevices object.
        // TODO(KaptenJansson) remove once implemented in Chrome stable.
        if (!navigator.mediaDevices.getUserMedia) {
            navigator.mediaDevices.getUserMedia = function(constraints) {
                return getUserMediaPromise_(constraints);
            };
        } else {
            // Even though Chrome 45 has navigator.mediaDevices and a getUserMedia
            // function which returns a Promise, it does not accept spec-style
            // constraints.
            var origGetUserMedia = navigator.mediaDevices.getUserMedia.
            bind(navigator.mediaDevices);
            navigator.mediaDevices.getUserMedia = function(cs) {
                return shimConstraints_(cs, function(c) {
                    return origGetUserMedia(c).then(function(stream) {
                        if (c.audio && !stream.getAudioTracks().length ||
                            c.video && !stream.getVideoTracks().length) {
                            stream.getTracks().forEach(function(track) {
                                track.stop();
                            });
                            throw new DOMException('', 'NotFoundError');
                        }
                        return stream;
                    }, function(e) {
                        return Promise.reject(shimError_(e));
                    });
                });
            };
        }

        // Dummy devicechange event methods.
        // TODO(KaptenJansson) remove once implemented in Chrome stable.
        if (typeof navigator.mediaDevices.addEventListener === 'undefined') {
            navigator.mediaDevices.addEventListener = function() {
                logging('Dummy mediaDevices.addEventListener called.');
            };
        }
        if (typeof navigator.mediaDevices.removeEventListener === 'undefined') {
            navigator.mediaDevices.removeEventListener = function() {
                logging('Dummy mediaDevices.removeEventListener called.');
            };
        }
    };

},{"../utils.js":14}],7:[function(require,module,exports){
  /*
   *  Copyright (c) 2017 The WebRTC project authors. All Rights Reserved.
   *
   *  Use of this source code is governed by a BSD-style license
   *  that can be found in the LICENSE file in the root of the source
   *  tree.
   */
  /* eslint-env node */
    'use strict';

    var SDPUtils = require('sdp');
    var utils = require('./utils');

    module.exports = {
        shimRTCIceCandidate: function(window) {
            // foundation is arbitrarily chosen as an indicator for full support for
            // https://w3c.github.io/webrtc-pc/#rtcicecandidate-interface
            if (!window.RTCIceCandidate || (window.RTCIceCandidate && 'foundation' in
                window.RTCIceCandidate.prototype)) {
                return;
            }

            var NativeRTCIceCandidate = window.RTCIceCandidate;
            window.RTCIceCandidate = function(args) {
                // Remove the a= which shouldn't be part of the candidate string.
                if (typeof args === 'object' && args.candidate &&
                    args.candidate.indexOf('a=') === 0) {
                    args = JSON.parse(JSON.stringify(args));
                    args.candidate = args.candidate.substr(2);
                }

                if (args.candidate && args.candidate.length) {
                    // Augment the native candidate with the parsed fields.
                    var nativeCandidate = new NativeRTCIceCandidate(args);
                    var parsedCandidate = SDPUtils.parseCandidate(args.candidate);
                    var augmentedCandidate = Object.assign(nativeCandidate,
                        parsedCandidate);

                    // Add a serializer that does not serialize the extra attributes.
                    augmentedCandidate.toJSON = function() {
                        return {
                            candidate: augmentedCandidate.candidate,
                            sdpMid: augmentedCandidate.sdpMid,
                            sdpMLineIndex: augmentedCandidate.sdpMLineIndex,
                            usernameFragment: augmentedCandidate.usernameFragment,
                        };
                    };
                    return augmentedCandidate;
                }
                return new NativeRTCIceCandidate(args);
            };
            window.RTCIceCandidate.prototype = NativeRTCIceCandidate.prototype;

            // Hook up the augmented candidate in onicecandidate and
            // addEventListener('icecandidate', ...)
            utils.wrapPeerConnectionEvent(window, 'icecandidate', function(e) {
                if (e.candidate) {
                    Object.defineProperty(e, 'candidate', {
                        value: new window.RTCIceCandidate(e.candidate),
                        writable: 'false'
                    });
                }
                return e;
            });
        },

        // shimCreateObjectURL must be called before shimSourceObject to avoid loop.

        shimCreateObjectURL: function(window) {
            var URL = window && window.URL;

            if (!(typeof window === 'object' && window.HTMLMediaElement &&
                'srcObject' in window.HTMLMediaElement.prototype &&
                URL.createObjectURL && URL.revokeObjectURL)) {
                // Only shim CreateObjectURL using srcObject if srcObject exists.
                return undefined;
            }

            var nativeCreateObjectURL = URL.createObjectURL.bind(URL);
            var nativeRevokeObjectURL = URL.revokeObjectURL.bind(URL);
            var streams = new Map(), newId = 0;

            URL.createObjectURL = function(stream) {
                if ('getTracks' in stream) {
                    var url = 'polyblob:' + (++newId);
                    streams.set(url, stream);
                    utils.deprecated('URL.createObjectURL(stream)',
                        'elem.srcObject = stream');
                    return url;
                }
                return nativeCreateObjectURL(stream);
            };
            URL.revokeObjectURL = function(url) {
                nativeRevokeObjectURL(url);
                streams.delete(url);
            };

            var dsc = Object.getOwnPropertyDescriptor(window.HTMLMediaElement.prototype,
                'src');
            Object.defineProperty(window.HTMLMediaElement.prototype, 'src', {
                get: function() {
                    return dsc.get.apply(this);
                },
                set: function(url) {
                    this.srcObject = streams.get(url) || null;
                    return dsc.set.apply(this, [url]);
                }
            });

            var nativeSetAttribute = window.HTMLMediaElement.prototype.setAttribute;
            window.HTMLMediaElement.prototype.setAttribute = function() {
                if (arguments.length === 2 &&
                    ('' + arguments[0]).toLowerCase() === 'src') {
                    this.srcObject = streams.get(arguments[1]) || null;
                }
                return nativeSetAttribute.apply(this, arguments);
            };
        },

        shimMaxMessageSize: function(window) {
            if (window.RTCSctpTransport || !window.RTCPeerConnection) {
                return;
            }
            var browserDetails = utils.detectBrowser(window);

            if (!('sctp' in window.RTCPeerConnection.prototype)) {
                Object.defineProperty(window.RTCPeerConnection.prototype, 'sctp', {
                    get: function() {
                        return typeof this._sctp === 'undefined' ? null : this._sctp;
                    }
                });
            }

            var sctpInDescription = function(description) {
                var sections = SDPUtils.splitSections(description.sdp);
                sections.shift();
                return sections.some(function(mediaSection) {
                    var mLine = SDPUtils.parseMLine(mediaSection);
                    return mLine && mLine.kind === 'application'
                        && mLine.protocol.indexOf('SCTP') !== -1;
                });
            };

            var getRemoteFirefoxVersion = function(description) {
                // TODO: Is there a better solution for detecting Firefox?
                var match = description.sdp.match(/mozilla...THIS_IS_SDPARTA-(\d+)/);
                if (match === null || match.length < 2) {
                    return -1;
                }
                var version = parseInt(match[1], 10);
                // Test for NaN (yes, this is ugly)
                return version !== version ? -1 : version;
            };

            var getCanSendMaxMessageSize = function(remoteIsFirefox) {
                // Every implementation we know can send at least 64 KiB.
                // Note: Although Chrome is technically able to send up to 256 KiB, the
                //       data does not reach the other peer reliably.
                //       See: https://bugs.chromium.org/p/webrtc/issues/detail?id=8419
                var canSendMaxMessageSize = 65536;
                if (browserDetails.browser === 'firefox') {
                    if (browserDetails.version < 57) {
                        if (remoteIsFirefox === -1) {
                            // FF < 57 will send in 16 KiB chunks using the deprecated PPID
                            // fragmentation.
                            canSendMaxMessageSize = 16384;
                        } else {
                            // However, other FF (and RAWRTC) can reassemble PPID-fragmented
                            // messages. Thus, supporting ~2 GiB when sending.
                            canSendMaxMessageSize = 2147483637;
                        }
                    } else if (browserDetails.version < 60) {
                        // Currently, all FF >= 57 will reset the remote maximum message size
                        // to the default value when a data channel is created at a later
                        // stage. :(
                        // See: https://bugzilla.mozilla.org/show_bug.cgi?id=1426831
                        canSendMaxMessageSize =
                            browserDetails.version === 57 ? 65535 : 65536;
                    } else {
                        // FF >= 60 supports sending ~2 GiB
                        canSendMaxMessageSize = 2147483637;
                    }
                }
                return canSendMaxMessageSize;
            };

            var getMaxMessageSize = function(description, remoteIsFirefox) {
                // Note: 65536 bytes is the default value from the SDP spec. Also,
                //       every implementation we know supports receiving 65536 bytes.
                var maxMessageSize = 65536;

                // FF 57 has a slightly incorrect default remote max message size, so
                // we need to adjust it here to avoid a failure when sending.
                // See: https://bugzilla.mozilla.org/show_bug.cgi?id=1425697
                if (browserDetails.browser === 'firefox'
                    && browserDetails.version === 57) {
                    maxMessageSize = 65535;
                }

                var match = SDPUtils.matchPrefix(description.sdp, 'a=max-message-size:');
                if (match.length > 0) {
                    maxMessageSize = parseInt(match[0].substr(19), 10);
                } else if (browserDetails.browser === 'firefox' &&
                    remoteIsFirefox !== -1) {
                    // If the maximum message size is not present in the remote SDP and
                    // both local and remote are Firefox, the remote peer can receive
                    // ~2 GiB.
                    maxMessageSize = 2147483637;
                }
                return maxMessageSize;
            };

            var origSetRemoteDescription =
                window.RTCPeerConnection.prototype.setRemoteDescription;
            window.RTCPeerConnection.prototype.setRemoteDescription = function() {
                var pc = this;
                pc._sctp = null;

                if (sctpInDescription(arguments[0])) {
                    // Check if the remote is FF.
                    var isFirefox = getRemoteFirefoxVersion(arguments[0]);

                    // Get the maximum message size the local peer is capable of sending
                    var canSendMMS = getCanSendMaxMessageSize(isFirefox);

                    // Get the maximum message size of the remote peer.
                    var remoteMMS = getMaxMessageSize(arguments[0], isFirefox);

                    // Determine final maximum message size
                    var maxMessageSize;
                    if (canSendMMS === 0 && remoteMMS === 0) {
                        maxMessageSize = Number.POSITIVE_INFINITY;
                    } else if (canSendMMS === 0 || remoteMMS === 0) {
                        maxMessageSize = Math.max(canSendMMS, remoteMMS);
                    } else {
                        maxMessageSize = Math.min(canSendMMS, remoteMMS);
                    }

                    // Create a dummy RTCSctpTransport object and the 'maxMessageSize'
                    // attribute.
                    var sctp = {};
                    Object.defineProperty(sctp, 'maxMessageSize', {
                        get: function() {
                            return maxMessageSize;
                        }
                    });
                    pc._sctp = sctp;
                }

                return origSetRemoteDescription.apply(pc, arguments);
            };
        },

        shimSendThrowTypeError: function(window) {
            if (!(window.RTCPeerConnection &&
                'createDataChannel' in window.RTCPeerConnection.prototype)) {
                return;
            }

            // Note: Although Firefox >= 57 has a native implementation, the maximum
            //       message size can be reset for all data channels at a later stage.
            //       See: https://bugzilla.mozilla.org/show_bug.cgi?id=1426831

            function wrapDcSend(dc, pc) {
                var origDataChannelSend = dc.send;
                dc.send = function() {
                    var data = arguments[0];
                    var length = data.length || data.size || data.byteLength;
                    if (dc.readyState === 'open' &&
                        pc.sctp && length > pc.sctp.maxMessageSize) {
                        throw new TypeError('Message too large (can send a maximum of ' +
                            pc.sctp.maxMessageSize + ' bytes)');
                    }
                    return origDataChannelSend.apply(dc, arguments);
                };
            }
            var origCreateDataChannel =
                window.RTCPeerConnection.prototype.createDataChannel;
            window.RTCPeerConnection.prototype.createDataChannel = function() {
                var pc = this;
                var dataChannel = origCreateDataChannel.apply(pc, arguments);
                wrapDcSend(dataChannel, pc);
                return dataChannel;
            };
            utils.wrapPeerConnectionEvent(window, 'datachannel', function(e) {
                wrapDcSend(e.channel, e.target);
                return e;
            });
        }
    };

},{"./utils":14,"sdp":2}],8:[function(require,module,exports){
  /*
   *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
   *
   *  Use of this source code is governed by a BSD-style license
   *  that can be found in the LICENSE file in the root of the source
   *  tree.
   */
  /* eslint-env node */
    'use strict';

    var utils = require('../utils');
    var filterIceServers = require('./filtericeservers');
    var shimRTCPeerConnection = require('rtcpeerconnection-shim');

    module.exports = {
        shimGetUserMedia: require('./getusermedia'),
        shimPeerConnection: function(window) {
            var browserDetails = utils.detectBrowser(window);

            if (window.RTCIceGatherer) {
                if (!window.RTCIceCandidate) {
                    window.RTCIceCandidate = function(args) {
                        return args;
                    };
                }
                if (!window.RTCSessionDescription) {
                    window.RTCSessionDescription = function(args) {
                        return args;
                    };
                }
                // this adds an additional event listener to MediaStrackTrack that signals
                // when a tracks enabled property was changed. Workaround for a bug in
                // addStream, see below. No longer required in 15025+
                if (browserDetails.version < 15025) {
                    var origMSTEnabled = Object.getOwnPropertyDescriptor(
                        window.MediaStreamTrack.prototype, 'enabled');
                    Object.defineProperty(window.MediaStreamTrack.prototype, 'enabled', {
                        set: function(value) {
                            origMSTEnabled.set.call(this, value);
                            var ev = new Event('enabled');
                            ev.enabled = value;
                            this.dispatchEvent(ev);
                        }
                    });
                }
            }

            // ORTC defines the DTMF sender a bit different.
            // https://github.com/w3c/ortc/issues/714
            if (window.RTCRtpSender && !('dtmf' in window.RTCRtpSender.prototype)) {
                Object.defineProperty(window.RTCRtpSender.prototype, 'dtmf', {
                    get: function() {
                        if (this._dtmf === undefined) {
                            if (this.track.kind === 'audio') {
                                this._dtmf = new window.RTCDtmfSender(this);
                            } else if (this.track.kind === 'video') {
                                this._dtmf = null;
                            }
                        }
                        return this._dtmf;
                    }
                });
            }
            // Edge currently only implements the RTCDtmfSender, not the
            // RTCDTMFSender alias. See http://draft.ortc.org/#rtcdtmfsender2*
            if (window.RTCDtmfSender && !window.RTCDTMFSender) {
                window.RTCDTMFSender = window.RTCDtmfSender;
            }

            var RTCPeerConnectionShim = shimRTCPeerConnection(window,
                browserDetails.version);
            window.RTCPeerConnection = function(config) {
                if (config && config.iceServers) {
                    config.iceServers = filterIceServers(config.iceServers);
                }
                return new RTCPeerConnectionShim(config);
            };
            window.RTCPeerConnection.prototype = RTCPeerConnectionShim.prototype;
        },
        shimReplaceTrack: function(window) {
            // ORTC has replaceTrack -- https://github.com/w3c/ortc/issues/614
            if (window.RTCRtpSender &&
                !('replaceTrack' in window.RTCRtpSender.prototype)) {
                window.RTCRtpSender.prototype.replaceTrack =
                    window.RTCRtpSender.prototype.setTrack;
            }
        }
    };

},{"../utils":14,"./filtericeservers":9,"./getusermedia":10,"rtcpeerconnection-shim":1}],9:[function(require,module,exports){
  /*
   *  Copyright (c) 2018 The WebRTC project authors. All Rights Reserved.
   *
   *  Use of this source code is governed by a BSD-style license
   *  that can be found in the LICENSE file in the root of the source
   *  tree.
   */
  /* eslint-env node */
    'use strict';

    var utils = require('../utils');
// Edge does not like
// 1) stun: filtered after 14393 unless ?transport=udp is present
// 2) turn: that does not have all of turn:host:port?transport=udp
// 3) turn: with ipv6 addresses
// 4) turn: occurring muliple times
    module.exports = function(iceServers, edgeVersion) {
        var hasTurn = false;
        iceServers = JSON.parse(JSON.stringify(iceServers));
        return iceServers.filter(function(server) {
            if (server && (server.urls || server.url)) {
                var urls = server.urls || server.url;
                if (server.url && !server.urls) {
                    utils.deprecated('RTCIceServer.url', 'RTCIceServer.urls');
                }
                var isString = typeof urls === 'string';
                if (isString) {
                    urls = [urls];
                }
                urls = urls.filter(function(url) {
                    var validTurn = url.indexOf('turn:') === 0 &&
                        url.indexOf('transport=udp') !== -1 &&
                        url.indexOf('turn:[') === -1 &&
                        !hasTurn;

                    if (validTurn) {
                        hasTurn = true;
                        return true;
                    }
                    return url.indexOf('stun:') === 0 && edgeVersion >= 14393 &&
                        url.indexOf('?transport=udp') === -1;
                });

                delete server.url;
                server.urls = isString ? urls[0] : urls;
                return !!urls.length;
            }
        });
    };

},{"../utils":14}],10:[function(require,module,exports){
  /*
   *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
   *
   *  Use of this source code is governed by a BSD-style license
   *  that can be found in the LICENSE file in the root of the source
   *  tree.
   */
  /* eslint-env node */
    'use strict';

// Expose public methods.
    module.exports = function(window) {
        var navigator = window && window.navigator;

        var shimError_ = function(e) {
            return {
                name: {PermissionDeniedError: 'NotAllowedError'}[e.name] || e.name,
                message: e.message,
                constraint: e.constraint,
                toString: function() {
                    return this.name;
                }
            };
        };

        // getUserMedia error shim.
        var origGetUserMedia = navigator.mediaDevices.getUserMedia.
        bind(navigator.mediaDevices);
        navigator.mediaDevices.getUserMedia = function(c) {
            return origGetUserMedia(c).catch(function(e) {
                return Promise.reject(shimError_(e));
            });
        };
    };

},{}],11:[function(require,module,exports){
  /*
   *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
   *
   *  Use of this source code is governed by a BSD-style license
   *  that can be found in the LICENSE file in the root of the source
   *  tree.
   */
  /* eslint-env node */
    'use strict';

    var utils = require('../utils');

    module.exports = {
        shimGetUserMedia: require('./getusermedia'),
        shimOnTrack: function(window) {
            if (typeof window === 'object' && window.RTCPeerConnection && !('ontrack' in
                window.RTCPeerConnection.prototype)) {
                Object.defineProperty(window.RTCPeerConnection.prototype, 'ontrack', {
                    get: function() {
                        return this._ontrack;
                    },
                    set: function(f) {
                        if (this._ontrack) {
                            this.removeEventListener('track', this._ontrack);
                            this.removeEventListener('addstream', this._ontrackpoly);
                        }
                        this.addEventListener('track', this._ontrack = f);
                        this.addEventListener('addstream', this._ontrackpoly = function(e) {
                            e.stream.getTracks().forEach(function(track) {
                                var event = new Event('track');
                                event.track = track;
                                event.receiver = {track: track};
                                event.transceiver = {receiver: event.receiver};
                                event.streams = [e.stream];
                                this.dispatchEvent(event);
                            }.bind(this));
                        }.bind(this));
                    }
                });
            }
            if (typeof window === 'object' && window.RTCTrackEvent &&
                ('receiver' in window.RTCTrackEvent.prototype) &&
                !('transceiver' in window.RTCTrackEvent.prototype)) {
                Object.defineProperty(window.RTCTrackEvent.prototype, 'transceiver', {
                    get: function() {
                        return {receiver: this.receiver};
                    }
                });
            }
        },

        shimSourceObject: function(window) {
            // Firefox has supported mozSrcObject since FF22, unprefixed in 42.
            if (typeof window === 'object') {
                if (window.HTMLMediaElement &&
                    !('srcObject' in window.HTMLMediaElement.prototype)) {
                    // Shim the srcObject property, once, when HTMLMediaElement is found.
                    Object.defineProperty(window.HTMLMediaElement.prototype, 'srcObject', {
                        get: function() {
                            return this.mozSrcObject;
                        },
                        set: function(stream) {
                            this.mozSrcObject = stream;
                        }
                    });
                }
            }
        },

        shimPeerConnection: function(window) {
            var browserDetails = utils.detectBrowser(window);

            if (typeof window !== 'object' || !(window.RTCPeerConnection ||
                window.mozRTCPeerConnection)) {
                return; // probably media.peerconnection.enabled=false in about:config
            }
            // The RTCPeerConnection object.
            if (!window.RTCPeerConnection) {
                window.RTCPeerConnection = function(pcConfig, pcConstraints) {
                    if (browserDetails.version < 38) {
                        // .urls is not supported in FF < 38.
                        // create RTCIceServers with a single url.
                        if (pcConfig && pcConfig.iceServers) {
                            var newIceServers = [];
                            for (var i = 0; i < pcConfig.iceServers.length; i++) {
                                var server = pcConfig.iceServers[i];
                                if (server.hasOwnProperty('urls')) {
                                    for (var j = 0; j < server.urls.length; j++) {
                                        var newServer = {
                                            url: server.urls[j]
                                        };
                                        if (server.urls[j].indexOf('turn') === 0) {
                                            newServer.username = server.username;
                                            newServer.credential = server.credential;
                                        }
                                        newIceServers.push(newServer);
                                    }
                                } else {
                                    newIceServers.push(pcConfig.iceServers[i]);
                                }
                            }
                            pcConfig.iceServers = newIceServers;
                        }
                    }
                    return new window.mozRTCPeerConnection(pcConfig, pcConstraints);
                };
                window.RTCPeerConnection.prototype =
                    window.mozRTCPeerConnection.prototype;

                // wrap static methods. Currently just generateCertificate.
                if (window.mozRTCPeerConnection.generateCertificate) {
                    Object.defineProperty(window.RTCPeerConnection, 'generateCertificate', {
                        get: function() {
                            return window.mozRTCPeerConnection.generateCertificate;
                        }
                    });
                }

                window.RTCSessionDescription = window.mozRTCSessionDescription;
                window.RTCIceCandidate = window.mozRTCIceCandidate;
            }

            // shim away need for obsolete RTCIceCandidate/RTCSessionDescription.
            ['setLocalDescription', 'setRemoteDescription', 'addIceCandidate']
                .forEach(function(method) {
                    var nativeMethod = window.RTCPeerConnection.prototype[method];
                    window.RTCPeerConnection.prototype[method] = function() {
                        arguments[0] = new ((method === 'addIceCandidate') ?
                            window.RTCIceCandidate :
                            window.RTCSessionDescription)(arguments[0]);
                        return nativeMethod.apply(this, arguments);
                    };
                });

            // support for addIceCandidate(null or undefined)
            var nativeAddIceCandidate =
                window.RTCPeerConnection.prototype.addIceCandidate;
            window.RTCPeerConnection.prototype.addIceCandidate = function() {
                if (!arguments[0]) {
                    if (arguments[1]) {
                        arguments[1].apply(null);
                    }
                    return Promise.resolve();
                }
                return nativeAddIceCandidate.apply(this, arguments);
            };

            // shim getStats with maplike support
            var makeMapStats = function(stats) {
                var map = new Map();
                Object.keys(stats).forEach(function(key) {
                    map.set(key, stats[key]);
                    map[key] = stats[key];
                });
                return map;
            };

            var modernStatsTypes = {
                inboundrtp: 'inbound-rtp',
                outboundrtp: 'outbound-rtp',
                candidatepair: 'candidate-pair',
                localcandidate: 'local-candidate',
                remotecandidate: 'remote-candidate'
            };

            var nativeGetStats = window.RTCPeerConnection.prototype.getStats;
            window.RTCPeerConnection.prototype.getStats = function(
                selector,
                onSucc,
                onErr
            ) {
                return nativeGetStats.apply(this, [selector || null])
                    .then(function(stats) {
                        if (browserDetails.version < 48) {
                            stats = makeMapStats(stats);
                        }
                        if (browserDetails.version < 53 && !onSucc) {
                            // Shim only promise getStats with spec-hyphens in type names
                            // Leave callback version alone; misc old uses of forEach before Map
                            try {
                                stats.forEach(function(stat) {
                                    stat.type = modernStatsTypes[stat.type] || stat.type;
                                });
                            } catch (e) {
                                if (e.name !== 'TypeError') {
                                    throw e;
                                }
                                // Avoid TypeError: "type" is read-only, in old versions. 34-43ish
                                stats.forEach(function(stat, i) {
                                    stats.set(i, Object.assign({}, stat, {
                                        type: modernStatsTypes[stat.type] || stat.type
                                    }));
                                });
                            }
                        }
                        return stats;
                    })
                    .then(onSucc, onErr);
            };
        },

        shimSenderGetStats: function(window) {
            if (!(typeof window === 'object' && window.RTCPeerConnection &&
                window.RTCRtpSender)) {
                return;
            }
            if (window.RTCRtpSender && 'getStats' in window.RTCRtpSender.prototype) {
                return;
            }
            var origGetSenders = window.RTCPeerConnection.prototype.getSenders;
            if (origGetSenders) {
                window.RTCPeerConnection.prototype.getSenders = function() {
                    var pc = this;
                    var senders = origGetSenders.apply(pc, []);
                    senders.forEach(function(sender) {
                        sender._pc = pc;
                    });
                    return senders;
                };
            }

            var origAddTrack = window.RTCPeerConnection.prototype.addTrack;
            if (origAddTrack) {
                window.RTCPeerConnection.prototype.addTrack = function() {
                    var sender = origAddTrack.apply(this, arguments);
                    sender._pc = this;
                    return sender;
                };
            }
            window.RTCRtpSender.prototype.getStats = function() {
                return this.track ? this._pc.getStats(this.track) :
                    Promise.resolve(new Map());
            };
        },

        shimReceiverGetStats: function(window) {
            if (!(typeof window === 'object' && window.RTCPeerConnection &&
                window.RTCRtpSender)) {
                return;
            }
            if (window.RTCRtpSender && 'getStats' in window.RTCRtpReceiver.prototype) {
                return;
            }
            var origGetReceivers = window.RTCPeerConnection.prototype.getReceivers;
            if (origGetReceivers) {
                window.RTCPeerConnection.prototype.getReceivers = function() {
                    var pc = this;
                    var receivers = origGetReceivers.apply(pc, []);
                    receivers.forEach(function(receiver) {
                        receiver._pc = pc;
                    });
                    return receivers;
                };
            }
            utils.wrapPeerConnectionEvent(window, 'track', function(e) {
                e.receiver._pc = e.srcElement;
                return e;
            });
            window.RTCRtpReceiver.prototype.getStats = function() {
                return this._pc.getStats(this.track);
            };
        },

        shimRemoveStream: function(window) {
            if (!window.RTCPeerConnection ||
                'removeStream' in window.RTCPeerConnection.prototype) {
                return;
            }
            window.RTCPeerConnection.prototype.removeStream = function(stream) {
                var pc = this;
                utils.deprecated('removeStream', 'removeTrack');
                this.getSenders().forEach(function(sender) {
                    if (sender.track && stream.getTracks().indexOf(sender.track) !== -1) {
                        pc.removeTrack(sender);
                    }
                });
            };
        },

        shimRTCDataChannel: function(window) {
            // rename DataChannel to RTCDataChannel (native fix in FF60):
            // https://bugzilla.mozilla.org/show_bug.cgi?id=1173851
            if (window.DataChannel && !window.RTCDataChannel) {
                window.RTCDataChannel = window.DataChannel;
            }
        },
    };

},{"../utils":14,"./getusermedia":12}],12:[function(require,module,exports){
  /*
   *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
   *
   *  Use of this source code is governed by a BSD-style license
   *  that can be found in the LICENSE file in the root of the source
   *  tree.
   */
  /* eslint-env node */
    'use strict';

    var utils = require('../utils');
    var logging = utils.log;

// Expose public methods.
    module.exports = function(window) {
        var browserDetails = utils.detectBrowser(window);
        var navigator = window && window.navigator;
        var MediaStreamTrack = window && window.MediaStreamTrack;

        var shimError_ = function(e) {
            return {
                name: {
                    InternalError: 'NotReadableError',
                    NotSupportedError: 'TypeError',
                    PermissionDeniedError: 'NotAllowedError',
                    SecurityError: 'NotAllowedError'
                }[e.name] || e.name,
                message: {
                    'The operation is insecure.': 'The request is not allowed by the ' +
                    'user agent or the platform in the current context.'
                }[e.message] || e.message,
                constraint: e.constraint,
                toString: function() {
                    return this.name + (this.message && ': ') + this.message;
                }
            };
        };

        // getUserMedia constraints shim.
        var getUserMedia_ = function(constraints, onSuccess, onError) {
            var constraintsToFF37_ = function(c) {
                if (typeof c !== 'object' || c.require) {
                    return c;
                }
                var require = [];
                Object.keys(c).forEach(function(key) {
                    if (key === 'require' || key === 'advanced' || key === 'mediaSource') {
                        return;
                    }
                    var r = c[key] = (typeof c[key] === 'object') ?
                        c[key] : {ideal: c[key]};
                    if (r.min !== undefined ||
                        r.max !== undefined || r.exact !== undefined) {
                        require.push(key);
                    }
                    if (r.exact !== undefined) {
                        if (typeof r.exact === 'number') {
                            r. min = r.max = r.exact;
                        } else {
                            c[key] = r.exact;
                        }
                        delete r.exact;
                    }
                    if (r.ideal !== undefined) {
                        c.advanced = c.advanced || [];
                        var oc = {};
                        if (typeof r.ideal === 'number') {
                            oc[key] = {min: r.ideal, max: r.ideal};
                        } else {
                            oc[key] = r.ideal;
                        }
                        c.advanced.push(oc);
                        delete r.ideal;
                        if (!Object.keys(r).length) {
                            delete c[key];
                        }
                    }
                });
                if (require.length) {
                    c.require = require;
                }
                return c;
            };
            constraints = JSON.parse(JSON.stringify(constraints));
            if (browserDetails.version < 38) {
                logging('spec: ' + JSON.stringify(constraints));
                if (constraints.audio) {
                    constraints.audio = constraintsToFF37_(constraints.audio);
                }
                if (constraints.video) {
                    constraints.video = constraintsToFF37_(constraints.video);
                }
                logging('ff37: ' + JSON.stringify(constraints));
            }
            return navigator.mozGetUserMedia(constraints, onSuccess, function(e) {
                onError(shimError_(e));
            });
        };

        // Returns the result of getUserMedia as a Promise.
        var getUserMediaPromise_ = function(constraints) {
            return new Promise(function(resolve, reject) {
                getUserMedia_(constraints, resolve, reject);
            });
        };

        // Shim for mediaDevices on older versions.
        if (!navigator.mediaDevices) {
            navigator.mediaDevices = {getUserMedia: getUserMediaPromise_,
                addEventListener: function() { },
                removeEventListener: function() { }
            };
        }
        navigator.mediaDevices.enumerateDevices =
            navigator.mediaDevices.enumerateDevices || function() {
                return new Promise(function(resolve) {
                    var infos = [
                        {kind: 'audioinput', deviceId: 'default', label: '', groupId: ''},
                        {kind: 'videoinput', deviceId: 'default', label: '', groupId: ''}
                    ];
                    resolve(infos);
                });
            };

        if (browserDetails.version < 41) {
            // Work around http://bugzil.la/1169665
            var orgEnumerateDevices =
                navigator.mediaDevices.enumerateDevices.bind(navigator.mediaDevices);
            navigator.mediaDevices.enumerateDevices = function() {
                return orgEnumerateDevices().then(undefined, function(e) {
                    if (e.name === 'NotFoundError') {
                        return [];
                    }
                    throw e;
                });
            };
        }
        if (browserDetails.version < 49) {
            var origGetUserMedia = navigator.mediaDevices.getUserMedia.
            bind(navigator.mediaDevices);
            navigator.mediaDevices.getUserMedia = function(c) {
                return origGetUserMedia(c).then(function(stream) {
                    // Work around https://bugzil.la/802326
                    if (c.audio && !stream.getAudioTracks().length ||
                        c.video && !stream.getVideoTracks().length) {
                        stream.getTracks().forEach(function(track) {
                            track.stop();
                        });
                        throw new DOMException('The object can not be found here.',
                            'NotFoundError');
                    }
                    return stream;
                }, function(e) {
                    return Promise.reject(shimError_(e));
                });
            };
        }
        if (!(browserDetails.version > 55 &&
            'autoGainControl' in navigator.mediaDevices.getSupportedConstraints())) {
            var remap = function(obj, a, b) {
                if (a in obj && !(b in obj)) {
                    obj[b] = obj[a];
                    delete obj[a];
                }
            };

            var nativeGetUserMedia = navigator.mediaDevices.getUserMedia.
            bind(navigator.mediaDevices);
            navigator.mediaDevices.getUserMedia = function(c) {
                if (typeof c === 'object' && typeof c.audio === 'object') {
                    c = JSON.parse(JSON.stringify(c));
                    remap(c.audio, 'autoGainControl', 'mozAutoGainControl');
                    remap(c.audio, 'noiseSuppression', 'mozNoiseSuppression');
                }
                return nativeGetUserMedia(c);
            };

            if (MediaStreamTrack && MediaStreamTrack.prototype.getSettings) {
                var nativeGetSettings = MediaStreamTrack.prototype.getSettings;
                MediaStreamTrack.prototype.getSettings = function() {
                    var obj = nativeGetSettings.apply(this, arguments);
                    remap(obj, 'mozAutoGainControl', 'autoGainControl');
                    remap(obj, 'mozNoiseSuppression', 'noiseSuppression');
                    return obj;
                };
            }

            if (MediaStreamTrack && MediaStreamTrack.prototype.applyConstraints) {
                var nativeApplyConstraints = MediaStreamTrack.prototype.applyConstraints;
                MediaStreamTrack.prototype.applyConstraints = function(c) {
                    if (this.kind === 'audio' && typeof c === 'object') {
                        c = JSON.parse(JSON.stringify(c));
                        remap(c, 'autoGainControl', 'mozAutoGainControl');
                        remap(c, 'noiseSuppression', 'mozNoiseSuppression');
                    }
                    return nativeApplyConstraints.apply(this, [c]);
                };
            }
        }
        navigator.getUserMedia = function(constraints, onSuccess, onError) {
            if (browserDetails.version < 44) {
                return getUserMedia_(constraints, onSuccess, onError);
            }
            // Replace Firefox 44+'s deprecation warning with unprefixed version.
            utils.deprecated('navigator.getUserMedia',
                'navigator.mediaDevices.getUserMedia');
            navigator.mediaDevices.getUserMedia(constraints).then(onSuccess, onError);
        };
    };

},{"../utils":14}],13:[function(require,module,exports){
  /*
   *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
   *
   *  Use of this source code is governed by a BSD-style license
   *  that can be found in the LICENSE file in the root of the source
   *  tree.
   */
    'use strict';
    var utils = require('../utils');

    module.exports = {
        shimLocalStreamsAPI: function(window) {
            if (typeof window !== 'object' || !window.RTCPeerConnection) {
                return;
            }
            if (!('getLocalStreams' in window.RTCPeerConnection.prototype)) {
                window.RTCPeerConnection.prototype.getLocalStreams = function() {
                    if (!this._localStreams) {
                        this._localStreams = [];
                    }
                    return this._localStreams;
                };
            }
            if (!('getStreamById' in window.RTCPeerConnection.prototype)) {
                window.RTCPeerConnection.prototype.getStreamById = function(id) {
                    var result = null;
                    if (this._localStreams) {
                        this._localStreams.forEach(function(stream) {
                            if (stream.id === id) {
                                result = stream;
                            }
                        });
                    }
                    if (this._remoteStreams) {
                        this._remoteStreams.forEach(function(stream) {
                            if (stream.id === id) {
                                result = stream;
                            }
                        });
                    }
                    return result;
                };
            }
            if (!('addStream' in window.RTCPeerConnection.prototype)) {
                var _addTrack = window.RTCPeerConnection.prototype.addTrack;
                window.RTCPeerConnection.prototype.addStream = function(stream) {
                    if (!this._localStreams) {
                        this._localStreams = [];
                    }
                    if (this._localStreams.indexOf(stream) === -1) {
                        this._localStreams.push(stream);
                    }
                    var pc = this;
                    stream.getTracks().forEach(function(track) {
                        _addTrack.call(pc, track, stream);
                    });
                };

                window.RTCPeerConnection.prototype.addTrack = function(track, stream) {
                    if (stream) {
                        if (!this._localStreams) {
                            this._localStreams = [stream];
                        } else if (this._localStreams.indexOf(stream) === -1) {
                            this._localStreams.push(stream);
                        }
                    }
                    return _addTrack.call(this, track, stream);
                };
            }
            if (!('removeStream' in window.RTCPeerConnection.prototype)) {
                window.RTCPeerConnection.prototype.removeStream = function(stream) {
                    if (!this._localStreams) {
                        this._localStreams = [];
                    }
                    var index = this._localStreams.indexOf(stream);
                    if (index === -1) {
                        return;
                    }
                    this._localStreams.splice(index, 1);
                    var pc = this;
                    var tracks = stream.getTracks();
                    this.getSenders().forEach(function(sender) {
                        if (tracks.indexOf(sender.track) !== -1) {
                            pc.removeTrack(sender);
                        }
                    });
                };
            }
        },
        shimRemoteStreamsAPI: function(window) {
            if (typeof window !== 'object' || !window.RTCPeerConnection) {
                return;
            }
            if (!('getRemoteStreams' in window.RTCPeerConnection.prototype)) {
                window.RTCPeerConnection.prototype.getRemoteStreams = function() {
                    return this._remoteStreams ? this._remoteStreams : [];
                };
            }
            if (!('onaddstream' in window.RTCPeerConnection.prototype)) {
                Object.defineProperty(window.RTCPeerConnection.prototype, 'onaddstream', {
                    get: function() {
                        return this._onaddstream;
                    },
                    set: function(f) {
                        var pc = this;
                        if (this._onaddstream) {
                            this.removeEventListener('addstream', this._onaddstream);
                            this.removeEventListener('track', this._onaddstreampoly);
                        }
                        this.addEventListener('addstream', this._onaddstream = f);
                        this.addEventListener('track', this._onaddstreampoly = function(e) {
                            e.streams.forEach(function(stream) {
                                if (!pc._remoteStreams) {
                                    pc._remoteStreams = [];
                                }
                                if (pc._remoteStreams.indexOf(stream) >= 0) {
                                    return;
                                }
                                pc._remoteStreams.push(stream);
                                var event = new Event('addstream');
                                event.stream = stream;
                                pc.dispatchEvent(event);
                            });
                        });
                    }
                });
            }
        },
        shimCallbacksAPI: function(window) {
            if (typeof window !== 'object' || !window.RTCPeerConnection) {
                return;
            }
            var prototype = window.RTCPeerConnection.prototype;
            var createOffer = prototype.createOffer;
            var createAnswer = prototype.createAnswer;
            var setLocalDescription = prototype.setLocalDescription;
            var setRemoteDescription = prototype.setRemoteDescription;
            var addIceCandidate = prototype.addIceCandidate;

            prototype.createOffer = function(successCallback, failureCallback) {
                var options = (arguments.length >= 2) ? arguments[2] : arguments[0];
                var promise = createOffer.apply(this, [options]);
                if (!failureCallback) {
                    return promise;
                }
                promise.then(successCallback, failureCallback);
                return Promise.resolve();
            };

            prototype.createAnswer = function(successCallback, failureCallback) {
                var options = (arguments.length >= 2) ? arguments[2] : arguments[0];
                var promise = createAnswer.apply(this, [options]);
                if (!failureCallback) {
                    return promise;
                }
                promise.then(successCallback, failureCallback);
                return Promise.resolve();
            };

            var withCallback = function(description, successCallback, failureCallback) {
                var promise = setLocalDescription.apply(this, [description]);
                if (!failureCallback) {
                    return promise;
                }
                promise.then(successCallback, failureCallback);
                return Promise.resolve();
            };
            prototype.setLocalDescription = withCallback;

            withCallback = function(description, successCallback, failureCallback) {
                var promise = setRemoteDescription.apply(this, [description]);
                if (!failureCallback) {
                    return promise;
                }
                promise.then(successCallback, failureCallback);
                return Promise.resolve();
            };
            prototype.setRemoteDescription = withCallback;

            withCallback = function(candidate, successCallback, failureCallback) {
                var promise = addIceCandidate.apply(this, [candidate]);
                if (!failureCallback) {
                    return promise;
                }
                promise.then(successCallback, failureCallback);
                return Promise.resolve();
            };
            prototype.addIceCandidate = withCallback;
        },
        shimGetUserMedia: function(window) {
            var navigator = window && window.navigator;

            if (!navigator.getUserMedia) {
                if (navigator.webkitGetUserMedia) {
                    navigator.getUserMedia = navigator.webkitGetUserMedia.bind(navigator);
                } else if (navigator.mediaDevices &&
                    navigator.mediaDevices.getUserMedia) {
                    navigator.getUserMedia = function(constraints, cb, errcb) {
                        navigator.mediaDevices.getUserMedia(constraints)
                            .then(cb, errcb);
                    }.bind(navigator);
                }
            }
        },
        shimRTCIceServerUrls: function(window) {
            // migrate from non-spec RTCIceServer.url to RTCIceServer.urls
            var OrigPeerConnection = window.RTCPeerConnection;
            window.RTCPeerConnection = function(pcConfig, pcConstraints) {
                if (pcConfig && pcConfig.iceServers) {
                    var newIceServers = [];
                    for (var i = 0; i < pcConfig.iceServers.length; i++) {
                        var server = pcConfig.iceServers[i];
                        if (!server.hasOwnProperty('urls') &&
                            server.hasOwnProperty('url')) {
                            utils.deprecated('RTCIceServer.url', 'RTCIceServer.urls');
                            server = JSON.parse(JSON.stringify(server));
                            server.urls = server.url;
                            delete server.url;
                            newIceServers.push(server);
                        } else {
                            newIceServers.push(pcConfig.iceServers[i]);
                        }
                    }
                    pcConfig.iceServers = newIceServers;
                }
                return new OrigPeerConnection(pcConfig, pcConstraints);
            };
            window.RTCPeerConnection.prototype = OrigPeerConnection.prototype;
            // wrap static methods. Currently just generateCertificate.
            if ('generateCertificate' in window.RTCPeerConnection) {
                Object.defineProperty(window.RTCPeerConnection, 'generateCertificate', {
                    get: function() {
                        return OrigPeerConnection.generateCertificate;
                    }
                });
            }
        },
        shimTrackEventTransceiver: function(window) {
            // Add event.transceiver member over deprecated event.receiver
            if (typeof window === 'object' && window.RTCPeerConnection &&
                ('receiver' in window.RTCTrackEvent.prototype) &&
                // can't check 'transceiver' in window.RTCTrackEvent.prototype, as it is
                // defined for some reason even when window.RTCTransceiver is not.
                !window.RTCTransceiver) {
                Object.defineProperty(window.RTCTrackEvent.prototype, 'transceiver', {
                    get: function() {
                        return {receiver: this.receiver};
                    }
                });
            }
        },

        shimCreateOfferLegacy: function(window) {
            var origCreateOffer = window.RTCPeerConnection.prototype.createOffer;
            window.RTCPeerConnection.prototype.createOffer = function(offerOptions) {
                var pc = this;
                if (offerOptions) {
                    if (typeof offerOptions.offerToReceiveAudio !== 'undefined') {
                        // support bit values
                        offerOptions.offerToReceiveAudio = !!offerOptions.offerToReceiveAudio;
                    }
                    var audioTransceiver = pc.getTransceivers().find(function(transceiver) {
                        return transceiver.sender.track &&
                            transceiver.sender.track.kind === 'audio';
                    });
                    if (offerOptions.offerToReceiveAudio === false && audioTransceiver) {
                        if (audioTransceiver.direction === 'sendrecv') {
                            if (audioTransceiver.setDirection) {
                                audioTransceiver.setDirection('sendonly');
                            } else {
                                audioTransceiver.direction = 'sendonly';
                            }
                        } else if (audioTransceiver.direction === 'recvonly') {
                            if (audioTransceiver.setDirection) {
                                audioTransceiver.setDirection('inactive');
                            } else {
                                audioTransceiver.direction = 'inactive';
                            }
                        }
                    } else if (offerOptions.offerToReceiveAudio === true &&
                        !audioTransceiver) {
                        pc.addTransceiver('audio');
                    }


                    if (typeof offerOptions.offerToReceiveAudio !== 'undefined') {
                        // support bit values
                        offerOptions.offerToReceiveVideo = !!offerOptions.offerToReceiveVideo;
                    }
                    var videoTransceiver = pc.getTransceivers().find(function(transceiver) {
                        return transceiver.sender.track &&
                            transceiver.sender.track.kind === 'video';
                    });
                    if (offerOptions.offerToReceiveVideo === false && videoTransceiver) {
                        if (videoTransceiver.direction === 'sendrecv') {
                            videoTransceiver.setDirection('sendonly');
                        } else if (videoTransceiver.direction === 'recvonly') {
                            videoTransceiver.setDirection('inactive');
                        }
                    } else if (offerOptions.offerToReceiveVideo === true &&
                        !videoTransceiver) {
                        pc.addTransceiver('video');
                    }
                }
                return origCreateOffer.apply(pc, arguments);
            };
        }
    };

},{"../utils":14}],14:[function(require,module,exports){
  /*
   *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
   *
   *  Use of this source code is governed by a BSD-style license
   *  that can be found in the LICENSE file in the root of the source
   *  tree.
   */
  /* eslint-env node */
    'use strict';

    var logDisabled_ = true;
    var deprecationWarnings_ = true;

    /**
     * Extract browser version out of the provided user agent string.
     *
     * @param {!string} uastring userAgent string.
     * @param {!string} expr Regular expression used as match criteria.
     * @param {!number} pos position in the version string to be returned.
     * @return {!number} browser version.
     */
    function extractVersion(uastring, expr, pos) {
        var match = uastring.match(expr);
        return match && match.length >= pos && parseInt(match[pos], 10);
    }

// Wraps the peerconnection event eventNameToWrap in a function
// which returns the modified event object.
    function wrapPeerConnectionEvent(window, eventNameToWrap, wrapper) {
        if (!window.RTCPeerConnection) {
            return;
        }
        var proto = window.RTCPeerConnection.prototype;
        var nativeAddEventListener = proto.addEventListener;
        proto.addEventListener = function(nativeEventName, cb) {
            if (nativeEventName !== eventNameToWrap) {
                return nativeAddEventListener.apply(this, arguments);
            }
            var wrappedCallback = function(e) {
                cb(wrapper(e));
            };
            this._eventMap = this._eventMap || {};
            this._eventMap[cb] = wrappedCallback;
            return nativeAddEventListener.apply(this, [nativeEventName,
                wrappedCallback]);
        };

        var nativeRemoveEventListener = proto.removeEventListener;
        proto.removeEventListener = function(nativeEventName, cb) {
            if (nativeEventName !== eventNameToWrap || !this._eventMap
                || !this._eventMap[cb]) {
                return nativeRemoveEventListener.apply(this, arguments);
            }
            var unwrappedCb = this._eventMap[cb];
            delete this._eventMap[cb];
            return nativeRemoveEventListener.apply(this, [nativeEventName,
                unwrappedCb]);
        };

        Object.defineProperty(proto, 'on' + eventNameToWrap, {
            get: function() {
                return this['_on' + eventNameToWrap];
            },
            set: function(cb) {
                if (this['_on' + eventNameToWrap]) {
                    this.removeEventListener(eventNameToWrap,
                        this['_on' + eventNameToWrap]);
                    delete this['_on' + eventNameToWrap];
                }
                if (cb) {
                    this.addEventListener(eventNameToWrap,
                        this['_on' + eventNameToWrap] = cb);
                }
            },
            enumerable: true,
            configurable: true
        });
    }

// Utility methods.
    module.exports = {
        extractVersion: extractVersion,
        wrapPeerConnectionEvent: wrapPeerConnectionEvent,
        disableLog: function(bool) {
            if (typeof bool !== 'boolean') {
                return new Error('Argument type: ' + typeof bool +
                    '. Please use a boolean.');
            }
            logDisabled_ = bool;
            return (bool) ? 'adapter.js logging disabled' :
                'adapter.js logging enabled';
        },

        /**
         * Disable or enable deprecation warnings
         * @param {!boolean} bool set to true to disable warnings.
         */
        disableWarnings: function(bool) {
            if (typeof bool !== 'boolean') {
                return new Error('Argument type: ' + typeof bool +
                    '. Please use a boolean.');
            }
            deprecationWarnings_ = !bool;
            return 'adapter.js deprecation warnings ' + (bool ? 'disabled' : 'enabled');
        },

        log: function() {
            if (typeof window === 'object') {
                if (logDisabled_) {
                    return;
                }
                if (typeof console !== 'undefined' && typeof console.log === 'function') {
                    console.log.apply(console, arguments);
                }
            }
        },

        /**
         * Shows a deprecation warning suggesting the modern and spec-compatible API.
         */
        deprecated: function(oldMethod, newMethod) {
            if (!deprecationWarnings_) {
                return;
            }
            console.warn(oldMethod + ' is deprecated, please use ' + newMethod +
                ' instead.');
        },

        /**
         * Browser detector.
         *
         * @return {object} result containing browser and version
         *     properties.
         */
        detectBrowser: function(window) {
            var navigator = window && window.navigator;

            // Returned result object.
            var result = {};
            result.browser = null;
            result.version = null;

            // Fail early if it's not a browser
            if (typeof window === 'undefined' || !window.navigator) {
                result.browser = 'Not a browser.';
                return result;
            }

            if (navigator.mozGetUserMedia) { // Firefox.
                result.browser = 'firefox';
                result.version = extractVersion(navigator.userAgent,
                    /Firefox\/(\d+)\./, 1);
            } else if (navigator.webkitGetUserMedia) {
                // Chrome, Chromium, Webview, Opera.
                // Version matches Chrome/WebRTC version.
                result.browser = 'chrome';
                result.version = extractVersion(navigator.userAgent,
                    /Chrom(e|ium)\/(\d+)\./, 2);
            } else if (navigator.mediaDevices &&
                navigator.userAgent.match(/Edge\/(\d+).(\d+)$/)) { // Edge.
                result.browser = 'edge';
                result.version = extractVersion(navigator.userAgent,
                    /Edge\/(\d+).(\d+)$/, 2);
            } else if (window.RTCPeerConnection &&
                navigator.userAgent.match(/AppleWebKit\/(\d+)\./)) { // Safari.
                result.browser = 'safari';
                result.version = extractVersion(navigator.userAgent,
                    /AppleWebKit\/(\d+)\./, 1);
            } else { // Default fallthrough: not supported.
                result.browser = 'Not a supported browser.';
                return result;
            }

            return result;
        }
    };

},{}]},{},[3])(3)
});